PNIVEB8ITY  OF  CALIFORNIA  PUBLICATIONS 

COLLEGE  OF  AGRICULTURE 
AGRICULTURAL  EXPERIMENT  STATION 

BERKELEY,   CALIFORNIA 


THE  COLD  STORAGE  OF  PEARS 


BY 

E.  L.  OVERHOLSER  AND  L.  P.  LATIMER 


BULLETIN  No.  377 

April,  1924 


UNIVERSITY  OF  CALIFORNIA  PRINTING  OFFICE 

BERKELEY 

1924 


Digitized  by  the  Internet  Archive 

in  2012  with  funding  from 

University  of  California,  Davis  Libraries 


http://www.archive.org/details/coldstorageofpea377over 


THE  COLD  STORAGE  OF  PEARS 

By  E.  L.  OVERHOLSER  and  L.  P.  LATIMER 


The  value  of  cold  storage  in  the  marketing  of  the  pear  lies 
primarily  in  prolonging  the  life  of  the  fruit,  and  thereby  extending 
the  period  of  marketability.  The  placing  of  a  part  of  the  pear  crop 
in  cold  storage,  temporarily,  to  remove  that  portion  from  the  market 
so  as  not  to  compete  with  the  remainder,  will  probably  become  a 
growing  practice. 

Pear  production  is  increasing  and  as  long  as  the  necessity  for 
disposing  of  the  entire  crop  as  soon  as  harvested  remains,  the  market 
in  some  years  may  be  overstocked  and  the  prices  low  during  the  '  *  peak 
period."  This  will  be  followed  by  a  shortage  of  fresh  pears  and 
higher  prices. 

According  to  Ramsey,  McKay,  Markell,  and  Bird22  it  would  be 
nearly  impossible  to  market  the  present  apple  crop  without  great  loss 
to  the  growers  and  consumers  except  for  the  aid  of  cold  storage.  The 
deciduous  fruit  that  can  probably  be  next  most  satisfactorily  cold- 
stored  is  the  pear. 

Certain  metabolic  activities  of  the  pear  continue  even  after  it  is 
picked — the  fruit  respires  or  takes  in  oxygen  from  the  air  and  gives 
off  carbon  dioxide  and  a  small  amount  of  water  vapor.  As  a  result 
of  the  metabolic  activities,  the  tissue  or  flesh  of  the  pear  gradually 
breaks  down,  becomes  dry  and  soft,  and  begins  to  decaj^.  These 
metabolic  processes  are  checked  and  the  final  breaking  down  of  the 
tissue  is  delayed  by  placing  the  fruit  in  low  temperatures,  which  do 
not  freeze  the  tissue. 

METHODS   OF   EXPERIMENTAL   PROCEDURE 

Experiments,  therefore,  have  been  conducted  to  determine  the 
effects  upon  the  storage  behavior  of  pears,  of  certain  factors,  as 
follows : 

a.  Storage  temperatures. 

b.  Maturity  of  fruit  when  harvested. 

c.  Pear  scald. 

d.  Penicillium. 

e.  Pollination. 

/.  Ammonia  fumes. 
g.  Loss  of  moisture. 


Z  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Furthermore,  the  comparative  keeping  qualities  of  different  varieties 
of  pears  in  cold  storage  have  been  observed. 

Handling  the  Fruit. — The  pears  were  picked,  carefully  placed  in 
boxes,  and  in  most  cases  brought  into  cold  storage  within  six  hours 
from  the  time  of  harvesting.  In  the  case  of  fruit  shipped  from  Davis 
and  other  points,  the  delay  was  short,  usually  not  more  than  twenty- 
four  hours. 

From  each  lot  as  received,  ten  specimens  were  taken  and  kept  at 
room  temperature  (65°  to  70°  F.)  to  ripen.  The  remainder  were 
divided  between  cold  storage  rooms  of  the  various  temperatures.  These 
temperatures  varied  no  more  than  2°  F.  at  any  time. 

Methods  of  Observation. — At  intervals  of  from  two  to  four  weeks, 
until  they  spoiled,  ten  pears  were  removed  from  each  cold  storage  lot 
and  placed  at  room  temperature.  Observations  upon  the  fruits  at 
room  temperature  were  made  every  two  or  three  days. 

At  each  observation  the  following  points  were  noted:  color  of 
epidermis,  color  of  flesh,  stage  of  ripeness,  flavor,  quality,  juiciness, 
defects;  days  required  for  ripening;  days  until  valueless;  general 
market  condition ;  and  additional  data  that  bore  upon  the  problem. 

Definition  of  Terms 

"Optimum  storage  period"  refers  to  the  latest  time  of  removal, 
which  gave  the  best  results  in  quality  and  time  of  holding  up  after 
removal  from  cold  storage. 

"Maximum  storage  period"  refers  to  the  time  beyond  which  it  was 
considered  unsafe  to  keep  the  fruit  in  storage,  because  of  the  likelihood 
of  loss  of  quality,  softening  of  texture,  susceptibility  to  rot  organisms, 
tendency  to  wilting,  and  rapidity  of  breakdown  after  removal,  though 
it  might  still  be  in  good  condition. 

"Degrees  of  ripeness"  were  indicated  by  the  following  terms: 

1.  hard  unripe  6.  medium  soft  rip™ 

2.  firm  unripe  7.  soft  ripe 

3.  firm  ripe  8.  past  ripe 

4.  medium  firm  ripe  9.  rotten 

5.  medium  ripe 

"Texture"  or  relative  juiciness  was  described  by  the  following 
terms : 

1.  unusually  juicy  4.  moderately  juicy. 

2.  very  juicy  5.  rather  dry 

3.  juicy 


Bulletin  377]  THe  COLD  STORAGE  OF  PEARS  3 

1 '  Quality ' '  or  pleasantness  of  flavor  was  described  by  the  following 
terms  : 

1.  excellent  5.  good  to  fair 

2.  very  good  6.  fair 

3.  good  to  very  good  7.  poor 

4.  good  8.  very  poor 

''Days  to  ripen"  refers  to  the  number  of  days  required  for  the 
fruit  to  attain  a  pleasing  edible  quality,  either  after  harvesting  or  after 
removal  from  the  storage  temperatures.  The  condition  corresponded 
to  the  degree  of  ripeness  termed  "medium  firm  ripe." 

"Failure  in  storage"  signified  the  condition  when  the  fruit, 
because  of  wilt,  the  growth  of  rot  organisms,  internal  breakdown,  and 
other  limiting  factors,  became  unfit  for  use. 

The  fruit  was  considered  valueless  when  ten  per  cent  or  more  of 
the  contents  of  a  box  became  unfit  for  market. 

EXPERIMENTAL   DATA 

The  data  concerning  the  behavior  of  varieties  of  pears  in  cold 
storage  and  the  factors  influencing  their  keeping  quality,  based  upon 
from  one  to  five  years'  work,  are  reported  herewith. 

EFFECT  OF  TEMPEKATUKE  UPON  THE  KEEPING  OF  PEAKS 

When  the  temperature  at  which  fruits  are  stored  is  low,  the  life 
processes  are  retarded,  but  they  do  not  cease,  even  though  the  tempera- 
ture is  the  lowest  at  which  the  fruit  can  be  safely  stored  without 
permanently  injuring  the  tissue.  Cold  storage  is  designed  to  check 
the  ripening  by  a  temperature  that  will  not  injure  the  fruit,  thereby 
prolonging  its  life. 

Palladin20  believes  that  respiration,  since  it  is  aided  by,  or  possibly 
entirely  dependent  upon  enzymes,  is  likely  to  be  most  active  at  about 
75°  F.  He  states  that  any  lowering  of  this  optimum  temperature  is 
followed  by  a  retardation  of  the  life  processes  of  the  organism.  The 
metabolic  activities  of  the  fruit,  which  are  a  part  of  its  life  processes, 
require  energy  that  is  largely  obtained  by  the  utilization  of  the  food 
materials  stored  within.  Since  low  temperatures  retard  these  meta- 
bolic activities,  the  life  period  of  the  fruit  is  correspondingly  pro- 
longed. This  is  the  basic  principle  upon  which  the  preservation  of 
fruit  by  means  of  low  cold  storage  temperatures  is  founded. 


4  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Workers  have  differed  with  respect  to  the  temperature  recom- 
mended for  storage  of  pears.  Cooper8  recommended  33°  F.,  and 
stated10  that  30°  F.  should  be  used  only  for  pears  to  be  kept  for  a 
long  time,  and  that  higher  temperatures  favor  quality.  Powell21 
recommended  that  pears  be  stored  at  a  temperature  of  about  32°  F., 
unless  it  was  desired  that  the  fruit  ripen  in  storage,  when  temperatures 
of  36°  F.  to  40°  F.,  or  even  higher,  may  be  advisable. 

Lewis,  et  al15  found  that  low  temperature  and  high  humidity,  and 
high  temperature  and  low  humidity,  were  harmful  to  the  ripening  of 
the  Bosc.  Furthermore,  Lewis,  Magness  and  Gate14  found  with  Bartletts 
that  transferring  pears  from  one  storage  temperature  to  colder  storage 
temperature  seemed  definitely  to  check  ripening  for  some  time.  They 
thought  that  suddenly  changing  the  fruit  from  warm  to  cold  storage 
after  the  ripening  processes  were  proceding  rapidly  checked  these 
processes  to  such  an  extent  that  ripening  became  slower  than  would 
be  the  case  had  the  fruit  been  put  in  cold  storage  soon  after  being 
removed  from  the  tree. 


TABLE  1 

The  Effect  of  Low  Temperatures  in  Checking  Ripening  of  Pears 


Temp,  of 

Storage 

Opl 

imum  Storage 

Maximum  Storage 

Vanity 

Days 

to  Opt. 

Storage 

Date 

Approx. 
Date 
Opt. 

Storage 

Days  Mar- 
ketable 

after 
Removal 
at  Opt. 

Stor.  Date 

Days 

to  Max. 

Stor. 

Date 

Approx. 
Date 
Max. 

Storage 

Days  Mar- 
ketable 
after 

Removal 
at  Max. 

Stor.  Date 

65°  F. 
45°  F. 
36°  F. 
32°  F. 
30°  F. 
65°  F. 
45°  F. 
36°  F. 
32°  F. 
30°  F. 
65°  F. 
45°  F. 
36°  F. 
32°  F. 
30°  F. 
65°  F. 
45°  F. 
36°  F. 
32°  F. 
30°  F. 

18 

33 

107 

115 

140 

18 

24 

107 

120 

125 

16 

31 

97 

92 

80 

10 

28 

99 

87 

68 

Sept.  16 
Oct.      1 
Dec.  15 
Dec.  23 
Jan.    17 
Aug.  27 
Sept.    3 
Dec.   18 
Dec.  31 
Jan.      5 
Sept.  15 
Oct.      1 
Dec.     6 
Dec.     1 
Nov.  19 
Aug.  20 
Sept.    7 
Nov.  22 
Nov.  10 
Oct.    22 

4 
5 
7 
8 
10 
6 
7 
7 
8 
9 
6 
8 
10 
10 
10 
5 
6 
7 
6 
6 

26 

49 

138 

159 

165 

25 

29 

138 

163 

170 

J9 

37 

134 

127 

120 

24 

34 

112 

121 

119 

Sept.  24 
Oct.    17 
Jan.    15 
Feb.      5 
Feb.   11 
Sept.    3 
Sept.    8 
Jan.    18 
Feb.    12 
Feb.   19 
Sept.  18 
Oct.      7 
Jan.    12 
Jan.      5 
Dec.  29 
Sept.    3 
Sept.  13 
Dec.     5 
Dec.   14 
Dec.   12 

3 

4 

5 

Anjou 

7 
8 

4 

4 

5 

5 

5 

Bosc  (0 

6 

Bosc  0) 

7 

Bosc  (') 

9 

Bosc  (') 

6 

Bosc  (') 

6 

Howell  (0 

4 

Howell  C1) .... 

4 

Howell  (i) 

5 

Howell  (J).... 

5 

Howell  (')  .  . 

5 

0)  Picked  before  proper  ripeness. 

Magness17  gives  30°  F.,  or  slightly  below,  as  the  best  storage  tem- 
perature for  Bartletts.  He  found  that  Bartletts  removed  to  tempera- 
tures of  60°  F.  to  70°  F.,  after  three  months  storage  at  28°  to  30°  F., 
ripened  satisfactorily  and  attained  high  quality. 


Bulletin  377]  THe  cold  STORAGE  OF  PEARS  5 

The  effect  of  low  temperatures  upon  the  keeping  of  pears  is  shown 
in  table  1.  In  the  investigations  reported  herewith,  pears  were  placed 
in  temperatures  of  30°,  32°,  36°,  45°  and  65°  F. 

The  data  in  table  1  indicate  that  pears  picked  at  the  proper  stage 
of  ripeness  can  be  safely  retained  in  storage  at  a  temperature  of  30°  F. 
The  fruit  kept  better  and  longer  than  at  any  of  the  higher  tempera- 
tures. There  is  danger,  however,  attending  storage  at  30°  F.,  in  that 
it  is  near  the  critical  temperature,  below  which  injury  to  the  fruit  or 
actual  freezing  occurs.  Wright  and  Taylor28  give  the  freezing  tem- 
perature of  Bartlett  pears  as  from  27.5°  F.  to  28.5°  F.  In  commercial 
cold  storage  plants,  with  the  difficulty  of  closely  regulating  the  tem- 
perature uniformly  throughout  large  rooms,  the  limits  for  tempera- 
ture fluctuations  might  not  be  sufficiently  great. 

A  temperature  of  32°  F.  was  found  to  be  satisfactory  except  where 
the  fruit  was  picked  fairly  green.  The  freezing  point  of  most  pears 
was  sufficiently  low  to  lessen  the  danger  of  storing  at  32°  F. 

It  is  interesting  to  note  that  fruit  picked  too  green  behaved  better 
in  storage  at  36°  F.  than  at  30°  F  or  32°  F.  At  lower  temperatures 
some  varieties,  when  green,  scalded  more  severely  when,  to  check 
transpiration  and  wilting,  the  humidity  was  raised  and  the  aeration 
was  lessened.  For  example,  the  Howell  at  30°  F.,  developed  a  con- 
siderable amount  of  scald  early  in  the  season.  Furthermore,  the  Bosc, 
picked  when  too  immature  did  not  ripen  properly  at  30°  F.  The  fruit 
either  developed  a  soft  rot  about  the  core,  or  wilted  and  remained  firm 
and  became  insipid  in  flavor.  At  36°  F.,  however,  similar  specimens 
of  Bosc  gradually  ripened  and  remained  in  marketable  condition, 
except  for  slight  wilting,  for  a  longer  period  of  time.  The  Forelle, 
Gray  Winter,  and  Vicar,  picked  when  relatively  immature,  also 
ripened  best  at  36°  F. 

When  green  fruit  was  stored  at  30°  F.,  each  week  accentuated 
slight  variations  in  the  original  degree  of  ripeness,  seemingly  because 
of  unequal  disturbances  of  the  various  ripening  processes  over  a  long 
period  of  time.  This  behavior  was  especially  noticeable  with  the 
Louise  variety.  The  Louise;  for  this  test  had  been  picked  prematurely 
and  was  green  when  stored.  It  ripened  satisfactorily  both  at  room 
temperature  and  at  a  temperature  of  36°  F.  Toward  the  end  of  its 
storage  period  at  30°  F.,  however,  the  lots  when  removed  exhibited 
various  stages  of  ripeness  from  the  yellow  blush  ripe  to  the  grass 
green,  hard  unripe  condition. 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


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Bulletin  377]  THe  COLD  STORAGE  OF  PEARS 


EFFECT  OF  DEGREE  OF  MATURITY  AT  TIME  OF  HARVEST 

Cooper10  found  that  Bartletts-  were  generally  picked  too  green  and 
tended  to  rot  at  the  core.  He11  suggested  that  the  fruit  should  be 
harvested  when  the  seeds  turn  brown. 

Stubenrauch  and  Ramsey24  found  that  Bartlett  pears  picked  when 
the  fruit  was  still  relatively  immature  deteriorated  more  rapidly  than 
when  picked  later.  They  found  that  by  leaving  the  fruit  on  the  trees 
about  two  weeks  longer,  the  season  could  be  extended  for  from  six  to 
seven  weeks.  The  suggestion  was  made  that  the  number  of  pickings 
should  be  sufficient  to  allow  all  the  fruit  to  mature  on  the  tree. 

Magness16  concluded  that  at  the  higher  temperatures  (70°  F)  early 
pickings  kept  longer  than  later  pickings.  At  40°  F.  storage,  the 
early  picked  fruits  scalded  and  became  brown  instead  of  ripening 
properly.  The  later  pickings,  however,  ripened  to  full  yellow  and 
prime  condition  with  almost  no  scald.  Late  picked  fruit  tended  to 
become  yellow  more  quickly  than  early  picked  fruit  but  remained 
firm  in  a  prime  eating  condition  for  a  longer  period  of  time. 

An  experiment  to  determine  the  effect  of  degree  of  ripeness  at  the 
time  of  harvest  upon  the  keeping  quality  in  cold  storage  and  upon 
appearance  and  flavor  was  conducted  by  the  writers. 

The  Hardy,  Bosc,  and  Cornice  from  the  Santa  Clara  Valley  were 
employed  and  were  stored  at  both  32°  F.  and  36°  F.  The  average 
cold  storage  behavior  for  the  four  seasons,  1919-20,  1920-21,  1921-22, 
and  1922-23,  of  the  three  varieties  as  influenced  by  the  stage  of 
development  when  picked  are  summarized  in  table  2.  The  height 
of  the  commercial  harvesting  period  conformed  to  the  second  picking 
of  each  variety. 

The  Bosc  Variety. — The  Bosc  generally  has  a  rich  golden  yellow 
skin  almost  entirely  covered  with  a  heavy  brown  or  cinnamon  russet. 
In  the  lots  observed,  however,  a  marked  variation  was  noted  in  the 
character  and  color  of  the  epidermis  of  the  pears  of  the  different 
pickings.  Even  after  ripening,  the  pears  of  the  first  picking  were 
only  a  pale  yellow  with  but  a  few  broken  streaks  of  brown  russet  on 
the  otherwise  smooth  surface  of  the  skin.  In  ripened  fruits  of  the 
third  and  fourth  picking,  the  color  was  a  rich  golden  yellow,  and  the 
epidermis  was  entirely  covered  with  a  cinnamon  russet.  The  pears  of 
the  second  picking,  made  at  the  height  of  the  commercial  harvest 
period,  were  intermediate  in  character  between  those  of  the  first  and 
of  the  third  and  fourth  pickings.  The  fruit  obtained  at  the  first  and 
second  pickings  was  small  and  insipid  in  flavor.     The  fruits  of  the 


8  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

third  and  fourth  pickings  were  larger,  the  flavor  sweeter  and  more 
aromatic,  and  the  quality  of  the  best. 

Behavior  at  32°  F.—At  32°  F.,the  third  and  fourth  pickings 
attained  the  best  quality  and  richest  flavor.  The  optimum  and 
maximum  storage  dates  were  latest  for  the  third  picking,  indicating 
that  this  picking  was  made  at  the  most  desirable  stage  of  maturity 
for  storage.  The  earlier  the  Bosc  was  picked,  the  greater  the  tendency 
for  the  variety  to  wilt  in  storage,  especially  in  the  long  fleshy  neck. 
There  was,  however,  pronounced  wilting  at  32°  F.,  with  specimens  of 
each  of  the  pickings  when  the  stem  was  injured  (fig.  1). 

Behavior  at  36°  F. — A  temperature  of  36°  F.  was  less  satisfactory 
for  storage  of  the  Bosc  than  32°  F.  The  Bosc  when  picked  at  the 
optimum  stage  of  development  kept  nearly  six  weeks  longer  at  32°  F. 
than  at  36°  F.  The  Bosc  specimens  picked  immaturely,  however, 
had  as  late  an  optimum  storage  date  at  36°  F.  as  at  32°  F.,  and 
likewise  kept  nearly  as  well  at  36°  F.  as  the  third  picking. 

Type  of  Failure. — At  32°  F.  the  Bosc,  especially  when  picked 
immaturely,  generally  failed  from  loss  of  moisture  and  wilting.  The 
later  pickings  did  not  wilt  so  badly,  but  the  tissue  became  soft  and 
failure  was  due  to  internal  breakdown.  At  36°  F.,  scald  was  the 
principal  cause  of  failure  and  some  rotting  developed  although  the 
Bosc  did  not  appear  to  be  especially  susceptible  to  the  growth  of  rot 
organisms. 

The  third  picking  of  Bosc,  made  about  ten  days  after  the  main 
commercial  picking  in  the  Santa  Clara  Valley,  attained  the  most 
characteristic  color,  size,  and  general  appearance,  and  kept  to  the 
latest  optimum  and  maximum  dates  in  storage  (fig.  2). 

The  Cornice  Variety. — The  first  picking  of  Cornice  was  made  when 
the  fruit  was  relatively  immature.  The  seeds  were  white  and  poorly 
developed,  the  flavor  insipid,  and  the  size  inferior.  The  pears  of  the 
second  picking  were  also  small.  They  were,  however,  better  colored 
and  did  not  wilt  so  badly  in  storage.  The  quality  attained  was  like- 
wise better,  the  flavor  being  sweeter,  and  the  flesh  more  juicy ;  the 
pears  were,  nevertheless,  below  the  standard  of  quality  for  the  Cornice. 
While  the  quality,  flavor,  texture,  and  juiciness  of  the  pears  of  the 
third  picking  were  better  than  at  the  previous  picking,  the  size  had 
only  increased  slightly.  The  fruit,  however,  appeared  to  be  more 
mature.  Cornice  pears  of  the  fourth  picking  were  well  colored,  with 
a  rich  yellow  ground  color  and  a  bright  reddish  overlay  on  one  side. 
The  quality  and  flavor  were  excellent.  The  size  was  nearly  double 
that  of  the  previous  pickings,  and  the  fruit  was  attractive  and  un- 


Bulletin  377] 


THE    COLD    STORAGE    OF   PEARS 


blemished.  The  pears  of  the  fifth  picking  closely  resembled  the  fourth, 
except  that  the  specimens  were  more  easily  bruised  and  thus  gave 
evidence  of  being  overripe  when  harvested. 


Fig.  1. — Bosc  pears  after  six  weeks'  storage,  showing  a  tendency  to  wilt, 
especially  when  the  stem  is  injured  (center  and  lower).  Normal  pear  (upper). 
The  photograph  was  made  at  an  early  stage  of  storage. 

Behavior  at  32°  F.  and  36°  F. — The  earlier  the  date  of  harvest  of 
the  first  four  pickings,  the  sooner  the  fruit  failed  in  storage,  both  at 
32°  F.  and  36°  P.     The  failure  of  the  first  three  pickings  largely 


10 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


resulted  from  wilting  and  scald.  To  a  less  extent,  scald  developed  with 
the  fourth  picking.  The  fifth  picking  exhibited  the  least  amount  of 
wilting  and  scald,  but  failed  in  storage  as  a  result  of  rotting  about 
the  bruised  areas  and  softening  and  breaking  down  of  the  flesh. 

During  certain  seasons,  the  last,  or  fifth  picking  of  Cornice,  actually 
kept  longer  at  32°  F.  than  the  earlier  pickings.  At  36°  F.,  however, 
the  fifth  picking  always  failed  in  advance  of  the  fourth  picking, 
indicating  that  overmaturity  is  more  serious  at  36°  F.  than  at  32°  F. 


\ 

k      -  j^Sfe; 

Mm 
■'-■■■  0M 

m\ 

B     |{|WgS^s 

|  jhi  i|imj  mii|  mi, 

i  m  r  1 1 1 1 1,|  H  1 1 1 1  m 

1  j  I  •  II 1 . 1 1 

lsj  M  II 

u,i«ii 

Fig.  2. — The  specimen  on  the  left  is  a  Bosc  pear  of  the  optimum  picking 
made  September  10.  The  one  on  the  right  is  of  the  commercial  picking  (Sep- 
tember 1).  The  photograph  taken  January  15,  illustrates  the  difference  in  size 
and  also  the  degree  of  wilting  when  stored  at  32°  F. 

The  pears  of  the  fourth  picking,  made  eleven  days  after  the  height 
of  the  commercial  harvest  period,  were  most  satisfactory  for  storage, 
as  indicated  by  the  following  characteristics:  (a)  Maximum  weight, 
and  size  nearly  double  that  attained  at  the  time  of  the  commercial 
picking;  (b)  excellent  quality,  sweet  flavor  and  fine,  melting,  juicy 
texture;  (c)  highly  colored,  attractive  fruit  which  retained  its  quali- 
ties for  over  five  months  in  storage  at  32°  F.,  and  which  remained 
marketable  for  over  two  weeks  after  becoming  ripe  subsequently  to 
removal  from  storage  (fig.  3). 


Bulletin  377]  THe  COLD  STORAGE  OF  PEARS  11 

The  Hardy  Variety. — The  first  and  second  pickings  were  undersized. 
The  third  picking  was  of  good  size,  but  the  fourth  and  fifth  pickings 
showed  a  marked  increase  in  size  of  the  fruit  (fig.  4).  The  flavor  of 
the  fruit  of  the  different  pickings  was  as  follows :  First,  acid  to  sub- 
acid and  insipid ;  second,  sub-acid  and  aromatic ;  third,  sweet  with 
almost  no  acidity.  The  pears  of  the  third  and  fourth  pickings  were 
very  juicy. 

Behavior  at  32°  F.  and  36°  F. — The  quality  attained  by  the  Hardy 
pears  stored  in  32°  F.  was  superior  to  that  developed  in  36°  F.  The 
pears  stored  at  32°  F.  were  more  juicy  than  pears  kept  at  36°  F.    At 


Fig.  3. — The  specimen  on  the  left  is  a  Cornice  pear  of  the  commercial  picking 
(September  10)  and  the  one  on  the  right  is  of  the  optimum  picking  made  Sep- 
tember 21.  The  photograph  taken  on  January  15,  illustrates  the  difference  in 
size  and  amount  of  wilting  when  stored  at  32°  F. 

32°  F.  the  first  three  pickings  failed  in  storage  because  of  wilting; 
the  fourth  and  fifth  pickings  failed  from  internal  breakdown  and  rot. 
At  36°  F.  the  first  two  pickings  wilted  and  scalded,  but  all  the  pick- 
ings were  inclined  to  become  rotten  before  wilting  resulted. 

The  commercial  picking  of  the  Hardy  in  the  Santa  Clara  Valley 
has  generally  been  completed  by  the  first  of  September,  or  previous 
to  the  second  picking  of  the  experiment.  The  fourth  picking,  made 
about  three  weeks  after  the  commercial  picking,  kept  best  in  storage 
at  both  temperatures.  The  third  picking,  made  ten  days  after  the 
commercial  picking,  however,  more  nearly  approached  the  keeping 


12 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


quality  of  the  fourth  picking  at  36°  F.  than  at  32°  F.  The  size  and 
flavor  of  the  fourth  picking  was  the  best.  The  first  and  second  pick- 
ings were  made  before  the  fruit  was  sufficiently  mature  for  harvest, 
as  evidenced  by  the  severe  wilting,  small  size,  and  inferior  flavor. 
The  fifth  picking,  while  of  large  size  and  good  quality,  was  made  too 
late  in  the  season  for  successful  storage  as  indicated  by  the  rapidity 
of  ripening,  breaking  down,  and  rotting. 


Fig.  4. — The  specimen  on  the  right  is  the  first  picking  of  Hardy  made 
August  22,  nine  days  previous  to  the  commercial  picking.  The  specimen  on  the 
left  is  from  the  optimum  picking  made  Septetmber  21.  Note  the  difference  in 
size  and  degree  of  wilting.  The  first  picking  never  became  marketable.  Photo- 
graph taken  January  15. 

Directions  for  Harvesting. — The  evidence  shows  that  immature 
pears  do  not  keep  so  well  as  those  which  are  firm  and  mature.  Obser- 
vations during  three  seasons  indicate  a  tendency  in  some  sections  of 
California  to  pick  pears  before  they  are  sufficiently  mature.  The 
texture,  flavor,  quality,  and  market  value  of  this  immature  fruit  do 
not  equal  that  of  the  better  developed,  properly  matured  fruit.  The 
fruit,  however,  must  not  remain  on  the  tree  long  enough  to  become 
overripe.  Such  fruit  is  nearer  the  end  of  its  life  limit  and  consequently 
deteriorates  with  even  greater  rapidity  in  cold  storage  than  immature 
fruit. 


Bulletin  377]  THe  COLD  STORAGE  OF  PEARS  13 

It  is  difficult  to  give  directions  that  will  enable  a  grower  satis- 
factorily to  determine  the  proper  time  each  season  to  harvest  his  pear 
crop.  Color,  especially  in  the  case  of  pears  which  have  a  red  blush, 
seems  to  be  correlated  with  maturity.  For  example,  it  is  noticeable 
that  such  pears  usually  wilt  or  shrivel  more  on  the  uncolored  side. 
As  the  pear  attains  maturity,  as  evidenced  by  the  fading  of  the  green 
or  deepening  of  the  yellow,  there  is  deposited  over  the  surface  a  layer 
of  cutin.  This  cutin  is  a  substance  only  slightly  permeable  to  water. 
It  acts  as  a  protective  wax-like  covering  and  prevents  the  loss  of 
water  through  the  skin;  and  may  also,  to  some  extent,  oppose  the 
entrance  of  rot  organisms. 

An  indication  of  the  best  stage  of  maturity  for  harvesting  pears  is 
the  shade  of  "ground"  color  of  the  fruit;  that  is,  the  color  which 
underlies  the  red  blush  in  the  case  of  colored  varieties,  or  the  surface 
color  of  varieties  that  develop  no  red.  The  ' '  ground ' '  color,  which  is 
immature,  becomes  lighter  in  shade  and  assumes  a  faint  yellowish 
tinge  as  the  fruit  approaches  maturity.  A  pronounced  yellow,  how- 
ever, usually  indicates  overmaturity. 

Murneek18  has  devised  a  special  apparatus  for  a  "pressure"  test 
which  appears  to  be  a  practical  means  of  measuring  the  stage  of 
ripeness  of  pears,  particularly  Bartletts.  He  found  that  harvesting 
of  Bartletts  under  Oregon  conditions  should  commence  when  the 
pressure  test  with  his  apparatus  indicated  an  average  resistance  of 
35  pounds.  The  lower  limit  at  which  it  is  safe  to  pick  Bartletts  is 
25  pounds.  The  Bosc,  according  to  Murneek,  during  its  picking 
season  should  register  20  to  24  pounds,  as  measured  by  his  method. 
Other  late  fall  or  winter  pears  show  different  figures. 


EFFECT  OF  PEAR  SCALD 

Pear  scald  is  a  dark  brown  or  blackened  condition  of  the  skin, 
generally  localized  at  first,  but  finally  involving  the  entire  surface  of 
the  fruit,  rendering  it  unfit  for  the  trade.  As  a  rule  the  scald  is 
superficial,  rarely  extending  more  than  one-eighth  of  an  inch  beneath 
the  surface.  The  authors  observe  that  a  peculiar  flavor  usually 
accompanies  scald  and  could  be  detected  before  the  tissues  showed 
any  discoloration. 

Pear  scald  is  the  result  of  unfavorable  cold  storage  conditions, 
although  maturity  and  weather  at  the  time  of  harvest,  delays  in 
storing,  and  methods  of  handling  also  affect  scald  development. 


14 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Temperature. — Observations  during  the  past  five  years  have  shown 
that  scald  occurs  when  pears  are  kept  at  temperatures  of  45°,  36°, 
32°,  and  30°  F.  Fruit  not  placed  in  cold  storage,  but  ripened  at  room 
temperatures,  did  not  develop  scald;  such  fruit  failed  from  internal 
breakdown,  wilt,  or  rot.  Pears  stored  at  the  higher  cold  storage 
temperatures,  especially  36°  F.,  scalded  more  severely  and  at  an  earlier 
date  than  fruit  of  the  same  lot  held  at  32°  or  30°  F. 

At  a  temperature  of  45°  F.,  before  scald  appeared,  the  quick 
germination  of  fungi  spores  and  their  subsequent  rapid  growth 
resulted  in  decay.  Table  3  shows  that  a  temperature  of  32°  F.,  as 
contrasted  with  36°  F.,  delayed  the  development  of  scald.  With 
Cornice  pears  the  delay  was  from  four  to  eight  weeks;  with  Bartletts 
about  six  weeks. 

TABLE  3 
Effect  of  Storage  Temperatures  upon  Development  of  Scald 


Date 
Picked 

Date  of  Development  of  Scald 

Variety 

32°  F. 

36°  F. 

Cornice 

Aug.  18 
Aug.  29 
Sept.    7 
Sept.  17 
Sept.  28 

Wilt  (no  scald) 

Jan.  10 

Wilt,  very  slight  scald 
Dec.  15. 

(t 

(I 

Mar.  10 

Jan.  7. 

it 

Feb.  10 

Jan.  1. 

a 

No  scald 

Bartlett  (selfed) 

Aug.  24 
Aug.  24 

Jan.  1 

Nov.  21. 

Bartlett  (crossed)  

Jan.  2 

Dec.  1. 

Aug.  18 
Aug.  29 
Sept.    7 
Sept.  17 
Aug.  18 
Aug.  27 
Sept.    7 

32°  F.        Cause  of  Failure        36°  F. 

Hardv 

Wilt 

Scald. 

a 

Wilt 

Scald. 

a 

Wilt 

Scald. 

u 

Rot 

Rot. 

Bosc 

Wilt;  breakdown.... 
Wilt;  breakdown.... 
Wilt;  breakdown.... 

Scald. 

It 

Scald. 

it 

Scald. 

Scald  frequently  occurred  at  36°  F. ;  at  32°  F.,  with  the  same 
varieties,  wilting  occurred  instead  of  scald.  In  this  respect  pear  scald 
is  analogous  to  apple  scald. 

Before  the  actual  appearance  of  scald  in  storage,  it  was  possible 
to  detect  a  peculiar  taste  in  the  fruit.  This  flavor  indicated  a  rapid 
subsequent  development  of  scald.     Furthermore,  fruit  at  this  stage, 


Bulletin  377] 


THE    COLD   STORAGE   OF   PEARS 


15 


even  though  showing  no  scald  in  storage,  developed  the  trouble  within 
four  or  five  daj^s  after  removal  to  room  temperature.  Thereafter  con- 
siderable scald  would  appear  in  storage. 

Maturity  at  Harvest. — The  effect  of  maturity  at  the  time  of  harvest 
on  susceptibility  to  scald  was  marked.  With  varieties  susceptible  to 
scald,  it  was  found  that  fruit  harvested  when  properly  matured  was 
less  subject  to  scald  than  when  picked  relatively  green,  or  overripe, 
as  shown  in  table  4  and  chart  I. 


TABLE  4 

Effect  of  Maturity  at  Time  of  Harvest  upon  the  Development  of  Scald  in 

Storage  (1921-22) 


Variety 

Days  to  failure  from  scald 

Maximum  storage  date 

32°  F. 

36°  F. 

32°  F. 

36°  F. 

Bartlett  (selfed) 

Aug.  24 
Sept.    6 
Sept.  16 

131 
132 
107 

88 

Jan.      1 
Jan.    15 
Jan.      1 

Oct.     21 

a 

a 

Cornice 

Aug.  18 

Aug.  29 

Sept.    7 
Sept.  17 
Sept.  20 

Wilt 

134 
183 
146 
Rot 

Wilt,  slight 
scald. 
108 
122 
106 
Rot 

Jan.    10 

Jan.    10 
Feb.  20 
Mar.    1 
Feb.  20 

Nov.    22 

n 

Dec.       1 

a 

Dec.     15 

it 

Dec.     22 

(< 

No  picking. 

Hardy 

Aug.  18 
Aug.  29 
Sept.    7 
Sept.  17 

Wilt 
Wilt 
Wilt 
Rot 

107 
125 
100 
Rot 

Jan.    15 
Jan.    15 
Feb.   15 
Jan.    15 

Nov.    10 

te 

Jan.        1 

it 

Dec.     15 
Nov.     15 

The  first  picking  of  Cornice  pears  wilted,  while  the  last  picking 
failed  from  rot.  The  Hardy  pears  likewise  showed  a  tendency  to  rot 
when  picked  late.  Magness17  states  that  the  earlier  picked  fruit  scalds. 
The  results  obtained  at  this  Station  showed  this  to  be  true  when 
excessive  wilting  did  not  occur. 

Table  4  also  shows  that  the  more  immature  fruit  generally  scalded 
sooner  after  harvest  than  did  the  properly  matured  fruit ;  over  mature 
fruit,  however,  scalded  more  rapidly  and  severely  than  either. 


Days   to  Failure   from  Scald 
388ig§3ig§§S§§g 


Bulletin  377]  The  COLD  STORAGE  OF  PEARS  17 

Certain  varieties  were  notably  more  susceptible  to  scald  than 
others.  Data  for  four  years  showed  the  Bartlett  to  be  most  subject 
to  scald  of  the  varieties  studied.  The  Cornice  was  next  and  was  closely 
followed  by  the  Louise  and  Clairgeau  in  degree  of  susceptibility. 
Furthermore,  such  varieties  as  the  Bordeaux  Vicar,  and  Pound,  of 
rather  low  quality  and  rarely  attaining  a  pleasing  eating  condition, 
were  found  to  be  subject  to  scald  in  storage.  The  Hardy  was  also 
sometimes  affected.  The  Easter  Beurre,  Forelle,  P.  Barry,  Anjou,  and 
other  long  keeping  varieties  on  the  other  hand  were  apparently 
immune. 

There  is  evidence  that  the  region  where  grown  may  have  some 
influence  on  the  occurrence  of  scald.  For  example,  most  pickings  of 
pears  grown  at  Santa  Clara,  California,  during  1922-23  showed  severe 
scalding  after  removal  from  storage  by  the  middle  of  January.  The 
Cornice  pears  obtained  from  Davis,  however,  did  not  show  signs  of 
scald  until  March  15.  Bartlett  pears  obtained  from  Antelope  Valley, 
having  an  elevation  of  3000  to  4000  feet  and  high  summer  tempera- 
tures kept  two  months  longer  without  scalding  than  those  grown  at 
Niles  near  the  coast. 

Another  interesting  feature  noted  was  the  manner  of  scalding  with 
the  Bordeaux  and  Pound  pears  in  the  box.  Upon  removing  them  from 
the  box  during  the  early  stages  of  scald,  it  was  noticed  that  the  pears 
first  scalded  where  they  had  been  in  contact  with  the  sides  of  the  box 
or  with  each  other. 

A  similar  effect  was  noted  in  the  case  of  the  same  two  varieties, 
and  also  of  the  Clairgeau  when  scalding  occurred  after  removal  from 
storage.  The  parts  of  the  fruit  lying  against  the  container  and  against 
one  another  scalded  first.  This  is  comparable  to  apple  scald  where 
ventilation  retards  the  development  of  the  trouble  by  permitting  the 
escape  of  the  injurious  gases  produced.7 

EFFECT  OF  BLUE  MOLD 

Blue  mold  (Penicillium  sps.)  may  seriously  affect  pears  in  storage 
and  is  the  principal  mold  making  appreciable  growth  at  temperatures 
of  32°  F. 

Varietal  Susceptibility. — Susceptibility  to  blue  mold  differed 
greatly  with  the  variety  of  pear.  The  Columbia,  Alencon,  and  Seckel, 
apparently  on  account  of  the  character  of  the  tissues  and  epidermis, 
were  relatively  immune  to  the  disease.  Columbia  pears  were  free  from 
blue  mold  infection  after  sixteen  months'  storage  at  32°  F.    However, 


18 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


after  this  period  of  storage  the  flesh  had  become  browned,  the  pulp 
dry,  and  the  quality  poor.  The  Seckel  pears  also  broke  down 
internally  rather  than  molded. 

The  Onondaga,  Flemish,  and  Diel  were  susceptible  to  attacks  by 
blue  mold  at  32°,  36°,  and  45°  F.  The  higher  the  temperature,  the 
greater  the  susceptibility;  this  trouble  was  generally  the  limiting 
factor  in  lessening  their  storage  period.  At  temperatures  of  36°  and 
45°  F.,  the  Easter  Beurre  was  also  susceptible  to  the  growth  of  blue 
mold  (fig.  5).  Other  varieties,  such  as  Urbaniste  and  Howell,  were 
susceptible,  under  certain  conditions,  but  not  to  the  same  degree. 


Fig.   5. — Easter  Beurre  pears   showing  characteristic  type   of  failure  in 
storage  at  36°  F.,  from  blue  mold  (Penicillium  expansum  Link). 


The  Winter  Nelis,  P.  Barry,  Forelle,  Hardy,  Cornice,  Bose,  and 
Glout  Morceau  were  midway  in  degree  of  resistance  as  contrasted  with 
the  groups  just  discussed,  although  they  were  attacked  under  con- 
ditions favorable  for  mold  growth. 

In  general,  all  varieties  molded  when  the  fruit  was  bruised  and 
sufficient  moisture  was  available. 

Temperature. — Brooks  and  Cooley,5  studying  the  development  of 
Penicillium  expansum  Link,  on  apples  found,  according  to  the  tem- 
perature, a  difference  (a)  in  time  necessary  for  infection  to  take  place; 


Bulletin  377] 


THE    COLD   STORAGE   OF   PEARS 


19 


and  (&)  in  the  rapidity  of  growth  thereafter  with  different  varieties. 
A  consistent  correlation  between  growth  and  temperature  in  general 
was  found  to  exist.  They  also  noted  that  at  32°  F.,  P.  expansum  made 
a  quicker  germination  and  more  rapid  early  growth  than  any  other 
fungus  studied.  They  stated  that  this  fact  helped  to  explain  its  common 
appearance  in  cold  storage.  They  found  that  68°  F.  was  optimum 
for  the  development  of  blue  mold.  At  86°  F.  on  the  Winesap,  growth 
was  scant. 

At  32°  F.  the  diameter  of  rot  caused  by  P.  expansum  was  10  mm., 
eight  weeks  after  inoculation;  while  at  41°  F.  the  diameter  of  rot  was 
55  mm.  It  took  more  than  two  weeks  for  the  rot  to  commence  growth 
below  50°  F.,  but  between  50°  F.  and  68°  F.  there  was  great  accelera- 
tion in  the  rate  of  development 

Eustace12  found  that  at  a  temperature  of  31°  F.  the  growth  of 
blue  mold  (P.  glaucum)  was  not  so  effectively  checked  as  that  of  other 
organisms  and  that  considerable  damage,  therefore,  resulted  in  cold 
storage  by  the  growth  of  this  fungus.  He  found  that  at  34.7°  F.  it 
took  about  twenty  times  as  long  for  the  spores  to  germinate  as  at 
71.6°  F.,  which  was  the  optimum  temperature. 

Blue  mold  occurred  at  all  temperatures  commonly  used  for  storing 
fruits.  At  the  lower  temperatures,  however,  the  growth  and  develop- 
ment of  blue  mold  spores  and  mycelium  was  so  retarded  that  the 
damage  to  fruits  from  a  commercial  standpoint  was  far  greater  at 
temperatures  of  36°  F.  and  above. 

The  data  obtained  by  the  writers  pertaining  to  the  effect  of  tem- 
perature upon  the  growth  of  blue  mold  are  given  in  table  5. 


TABLE  5 

Effect  of  Storage  Temperature  upon  the  Growth  of  Blue  Mold 

(Penicillium  sps.)  on  Pears  (1921-22) 


Variety 


Tempera- 
ture 

Date  value- 
less from 
blue  mold 
growth 

32°  F. 

No  mold 

36°  F. 

Nov.  21 

32°  F. 

Jan.     1 

36°  F. 

Dec.  10 

32°  F. 

Apr.     1 

36°  F. 

Jan.    10 

32°  F. 

No  mold 

36°  F. 

Feb.  10 

Date  of  maximum 
storage 


Bartlett  (selfed) 
Bartlett  (selfed) 

Onondaga 

Onondaga 

Diel 

Diel 

Easter 

Easter 


Jan.  1  (scald) 
Nov.  21 
Jan.  1 
Dec.  10 
Apr.  1 
Jan.  10 
May  1 
Feb.  10 


20  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT   STATION 

Selfed  Bartlett  pears  of  the  first  picking  at  36°  F.  showed  growth 
of  blue  mold  by  November  21,  while  at  32°  F.  no  mold  occurred; 
failure  at  that  temperature,  however,  resulted  from  scald  on  January  1. 
Upon  the  Onondaga,  blue  mold  developed  twenty  days  later  at  32°  F. 
than  at  36°  F.,  while  upon  the  Diel  it  was  delayed  about  eighty  days. 
With  the  Easter  at  36°  F.,  mold  developed  by  February  10,  while  at 
32°  F.  no  mold  had  occurred  as  late  as  May  1. 

Maturity  at  Time  of  Harvest. — Late  pickings  were  generally  more 
susceptible  to  blue  mold  than  earlier  pickings.  Earlier  pickings  of 
Easter  Beurre  pears  developed  no  mold,  while  late  pickings  were  quite 
subject  to  the  rot.  The  early  picked  fruit  tended  to  wilt  and  this 
lessened  the  occurrence  of  mold,  probably  because  of  the  lack  of 
favorable  moisture  conditions. 

At  32°  F.,  during  the  1922-23  season,  the  Bloodgood  picked  July  6 
failed  from  wilt  October  20 ;  the  second  picking,  July  13,  failed  from 
blue  mold  December  1.  In  general,  it  was  only  the  latest  picked  fruit 
that  molded  badly. 

Wounds,  bruises,  and  delay  in  getting  into  storage  greatly  increased 
the  damage  from  Penicillium  sps.  Most  varieties  possessing  a  tough, 
well  cutinized  epidermis,  free  from  bruises  or  scars,  were  rarely 
destroyed  by  mold  in  storage.  Specimens  of  the  same  varieties,  how- 
ever, with  skin  punctures  developed  blue  mold.  In  addition  the 
developing  rot  and  exuding  juice  produced  conditions  so  favorable 
for  mold  growth  that  adjacent  sound  fruits  also  became  quickly 
infected. 

These  observations  are  borne  out  by  other  investigators.  Brooks, 
Co'oley,  and  Fisher7  working  with  apples,  state  that  the  germ  tubes  of 
blue  mold  did  not  penetrate  the  sound  skin  of  the  fruit,  but  gained 
entrance  through  wounds  resulting  from  mechanical  injury  or  from 
insects.  However,  when  a  sound  apple  was  imbedded  in  the  remains 
of  a  rotten  one  the  disease  apparently  penetrated  the  skin  without  a 
puncture. 

Delay  in  storing  after  harvest  hastened  the  time  when  fruit  in  cold 
storage  was  rendered  unfit  by  mold.  Brooks  and  Cooley5  showed  that 
fruit  picked  and  inoculated  October  19  by  puncture  with  the  spores 
of  blue  mold  and  placed  in  storage  immediately  at  32°  F.  developed 
no  rot  as  late  as  February  28.  However,  when  storage  was  delayed 
seven  days  after  inoculation,  considerable  rot  had  developed  by 
February  28.  This  resulted  because  the  spores  had  developed  suffi- 
ciently at  the  higher  temperature  previous  to  storage  to  permit 
subsequent  growth  after  being  stored. 


Bulletin  377] 


the  cold  storage  op  pears 


21 


EFFECT  OF  POLLINATION 

Bartlett  pears  in  the  Antelope  Valley  frequently  set  fruit  partheno- 
carpically  or  without  the  development  of  seeds.  Certain  growers  of 
that  section  have  in  some  instances  been  opposed  to  provision  for  cross- 
pollination,  because  they  felt  that  seed  development  lessened  the 
keeping  quality  of  the  fruit. 


Chart  II. — Showing  the  keeping  quality  of  seeded  and  seedless  Bartlett 

pears  at  storage  temperatures  of  32°  and  36°  F. 

"Op,"  optimum  storage  date;  "M,"  maximum  storage  date. 

During  the  season  of  1921-22,  tests  were  conducted  to  determine 
the  effect  of  pollination  upon  the  keeping  quality.  Bartlett  pears  were 
obtained  from  Littlerock,*  a  desert  region  of  from  3000  to  4000  feet 
elevation.  Three  different  pickings  were  made  of  both  hand-crossed 
fruit  (Bartlett  x  Winter  Nelis)  and  fruit  which  had  set  partheno- 
carpically  (self  pollinated).  The  data  obtained  are  presented  in 
table  6  and  in  chart  II. 


*  The  writers  desire  to  express  thanks  to  Mr.  M.  W.  Dula,  who  made  the 
hand  crosses  of  Winter  Nelis  upon  Bartlett  and  who  supplied  the  fruit  from 
Littlerock,  California. 


22 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT   STATION 


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Bulletin  377]  THe  COLD  STORAGE  OF  PEARS  23 

Observations. — The  cross-pollinated  pears,  because  of  the  large 
amount  of  tissue  comprising  the  core,  had  less  edible  flesh  than  the 
fruit  which  set  parthenocarpically  (fig.  6). 

The  data  showed  that  the  crossed  Bartletts  matured  earlier  than 
the  selfed  fruit.  This  was  indicated  by  the  fact  that  at  36°  F.,  on 
November  16,  the  box  of  first  picking  of  selfed  pears  showed  scalding 
to  the  extent  of  from  95  to  98  per  cent,  whereas  the  crossed  Bartletts 
had  just  begun  to  scald.  Later  in  the  season  it  was  found  that  the 
selfed  Barletts  at  32°  F.  showed  scalding  fully  three  weeks  before  the 
crossed  Bartletts. 


Fig.  6. — Bartlett  pears  self-pollinated   (left),   cross-pollinated    (right), 
showing  the  relative  proportion  of  edible  tissue  in  each. 

Facts  tending  to  confirm  the  belief  that  the  selfed  pears  matured 
more  slowly  on  the  tree  than  the  crossed  pears  were  as  follows :  (a)  The 
early  date  of  scalding  indicated  immaturity,  (b)  The  crossed  Bart- 
letts colored  and  ripened  in  storage  before  the  selfed.  (c)  The  first 
pickings  of  crossed  pears  kept  better  than  the  first  picking  of  selfed, 
because  the  former  were  nearer  the  proper  stage  of  maturity  while 
the  latter  were  immature.  The  last  picking  of  the  crossed  pears 
kept  but  a  relatively  short  time,  because  they  were  approaching  over- 
ripeness,  while  the  selfed  were  still  at  the  proper  stage  of  maturity. 

The  facts  indicate  that  the  crossed  pears  were  in  an  optimum 
condition  for  storing  at  a  time  midway  between  the  first  and  second 
pickings.  The  selfed  Bartletts  were  in  an  optimum  condition  for 
storing  two  weeks  later,  at  a  time  when  the  crossed  pears  were  too 
mature  for  successful  storage. 


24  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

The  results  showed  that  with  the  early  picked  fruit,  the  cross- 
pollinated  pears  kept  the  longest.  Wth  fruit  picked  relatively  late, 
however,  the  self -pollinated  pears  had  an  optimum  date  nearly  two 
months  later  and  a  maximum  date  two  weeks  later. 

A  difference  in  methods  of  spoiling  was  noted.  The  breakdown  in 
selfed  pears,  which  were  removed  from  storage  and  ripened,  was 
characterized  by  a  browning  and  softening  of  the  tissue  commencing 
at  the  surface  of  the  fruit  and  progressing  inwardly  until  the  entire 
specimen  was  spoiled.  The  cross-pollinated  specimens  broke  down  at 
the  core  first,  and  the  browning  and  softening  of  the  tissue  progressed 
outwardly. 

Apparently  crossed  pears  should  be  picked  about  two  weeks 
earlier  than  selfed  pears.  The  difference  between  the  shapes  of  crossed 
and  selfed  Bartletts  (fig.  7)  aids  in  distinguishing  them.  At  each 
picking  only  pears  of  a  uniform  stage  or  ripeness,  which  are  sufficiently 
mature,  should  be  harvesetd. 

EFFECT   OF  AMMONIA  FUMES  UPON  PEAKS 

Anhydrous  ammonia  is  the  g*as  most  frequently  employed  to  obtain 
refrigeration.  Notwithstanding  care  exercised  by  men  in  charge  of 
plants,  leaks  may  occur  with  certain  types  of  equipment,  and  ammonia 
fumes  may  thus  unavoidably  gain  entrance  to  storage  rooms.  Hence 
it  becomes  of  interest  to  note  the  effect  of  ammonia  gas  upon  the  fruit. 

Pears  contain  a  substance  that  behaves  similarly  to  a  vegetable 
litmus  by  becoming  dark  when  alkaline  and  colorless  when  acid.  The 
behavior  is  apparently  similar  to  that  found  for  apples  by  Overholser 
and  Cruess.19  Ammonia  gas  gives  alkaline  reaction.  Since  the  fumes 
are  quite  soluble  in  fruit  juices,  they  may  be  absorbed  through  the 
lenticel-like  openings,  or  ' '  dots ' '  of  the  epidermis,  sufficiently  to  bring 
about  an  alkaline  condition  in  local  areas. 

The  oxidation  processes  in  pears  also  proceed  more  rapidly  when 
the  medium  is  slightly  alkaline  than  when  it  is  acid,  as  is  normally  the 
case  with  the  tissues  of  pears.  Furthermore,  the  concentration  of 
ammonia  may  become  sufficiently  great  to  act  deleteriously  by  increas- 
ing the  permeability  of  the  cells  and  thus  disorganizing  the  protoplasm 
and  permitting  the  mixing  of  the  oxidizing  enzyme  and  substrate. 
Hence  fruit  subjected  to  ammonia  gas  or  fumes  may  also  darken  by 
oxidation,  but  the  discoloration  thus  produced  is  apparently  distinct 
from  that  immediately  effected  by  alkalinity.  The  two  colors,  however, 
are  inseparable  upon  the  basis  of  appearance. 


Bulletin  377] 


THE  COLD  STORAGE  OF  PEARS 


25 


Fig.  7. — Self -pollinated  Bartlett  pear  (left),  cross  pollinated  specimen 
(right),  showing  characteristic  shape  of  each. 


it. 


V 


Fig.  8. — Vicar  pear  (left)  and  Col.  Wilder  (right),  showing  the  effect  of 
ammonia  fumes  upon  firm  unripe  fruit. 


26 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT   STATION 


Figure  8  shows  the  characteristic  appearance  of  pears  subjected  to 
ammonia  gas.  The  cells  immediately  adjacent  to  the  lenticel-like 
opening's  of  the  epidermis  first  exhibited  crimson  colored  rings  about 
the  lenticels  that  quickly  became  black.  The  depth  of  penetration, 
except  upon  prolonged  exposure,  was  from  three  to  five  layers  of  cells. 
Upon  continued  exposure  for  from  five  to  seven  days,  darkening  took 
place  to  a  depth  of  one-half  inch,  although  the  fibro-vascular  bundles 
were  darkened  to  a  greater  depth. 

Effect  of  Stage  of  Maturity  when  Harvested. — Cornice  pears  picked 
at  four  different  stages  of  maturity  were  exposed  to  ammonia  fumes. 
The  later,  better  matured  pickings  were  more  slowly  affected  than  were 
the  earlier  pickings,  as  shown  in  table  7. 

TABLE  7 

Effect  of  Maturity  of  Comice  Pears  when  Harvested  upon  Susceptibility  to 

Ammonia  Fumes 


Picking 

Date 
Harvested 

Time  for  first 

dark  spots  to 

appear 

Time  for 

numerous 

spots 

Time  for  general 

darkening  of 
surface  to  occur 

1st 

Aug.  18 
Sept.    7 
Sept.  17 
Sept.  28 

60  minutes 

75  minutes 

125  minutes 

195  minutes 

125  minutes 
115  minutes 
195  minutes 
None 

140  minutes 

2nd 

146  minutes 

3rd 

210  minutes 

4th 

285  minutes 

Similar  observations  with  other  varieties  indicated  that  pears 
picked  in  a  green  condition  were  more  seriously  affected  by  ammonia 
fumes  than  specimens  picked  in  a  more  ripened  state. 

Histological  examination  of  the  epidermis  of  the  different  pickings 
of  Comice  did  not  show  any  significant  variation  in  the  thickness  of 
deposition  of  cutin  or  in  the  size  of  the  lenticel-like  openings.  There 
was  a  difference  in  the  number  of  lenticels  per  square  centimeter, 
averaging  35  in  the  first  picking  and  27  in  the  fourth.  This,  however, 
would  not  appreciably  affect  the  rapidity  of  darkening  of  tissue  about 
the  individual  openings.  Nevertheless,  the  lessened  rapidity  of  pene- 
tration of  the  ammonia  gas  in  the  case  of  the  later  pickings  indicate  a 
more  complete  sealing  of  the  epidermis  as  maturity  progressed. 

Difference  in  Varietal  Susceptibility. — Four  pickings  each  of 
Hardy  and  Comice  were  contrasted  with  respect  to  the  varietal  sus- 
ceptibility to  ammonia  fumes.  The  time  required  for  the  effect  to 
become  apparent  was  averaged  for  the  four  pickings  of  each  variety, 
as  shown  in  table  8. 


Bulletin  377] 


THE    COLD    STORAGE   OF    PEARS 


27 


TABLE  8 

Difference  in  Varietal  Susceptibility  of  Comtce  and  Hardy  Pears  to 

Ammonia  Fumes  (Average  of  Four  Pickings) 


Variety 


Average  time  for 

first  dark  spots 

to  appear 


Average  time  for 

general  darkening 

of  surface  to 


Average  area  of 

lenticel  openings 

in  epidermis 


Average  frequency 
of  lenticel 
openings 


Cornice. 
Hardy.. 


132  minutes 
42       " 


213  minutes 
51 


.063  sq.  mm. 
.30      "       " 


31  per  sq.  mm. 
21    "     "       " 


The  Hardy  showed  a  more  rapid  penetration  of  the  ammonia  fumes 
than  the  Cornice.  The  lenticel  areas  of  the  Hardy  darkened  over  three 
times  as  rapidly  as  the  Cornice,  and  the  entire  epidermis  was  blackened 
about  four  times  as  rapidly,  indicating  that  the  absorption  proceeded 
at  an  accelerated  rate.  Furthermore,  the  Cornice  exhibited  an  inter- 
mediate stage  where  the  black  dots  became  numerous,  and  subsequently 
the  entire  epidermis  darkened.  The  entire  epidermis  of  the  Hardy, 
however,  quickly  darkened  after  the  appearance  of  the  first  black  dots. 

This  difference  in  varietal  susceptibility  may  be  accounted  for  by 
the  fact  that  the  lenticel-like  openings  of  the  Hardy  were  nearly  five 
times  the  diameter  of  those  of  the  Cornice.  Furthermore,  the  thickness 
of  cutin  covering  the  epidermis  of  the  Hardy  was  about  one-third  that 
of  the  Cornice,  and  the  evidence  indicated  that  the  ammonia  fumes 
penetrated  the  layer  of  cutin  in  the  Hardy. 

The  presence  of  moisture  increased  the  seriousness  of  the  effects  of 
ammonia  fumes.  Pears  that  were  badly  wilted  and  which  had  a  dry 
surface  were  not  so  susceptible  to  ammonia  fumes  as  those  with  a  moist 
surface. 

LOSS  OF  MOISTURE  IN  RIPENING 

Interesting  data  pertaining  to  decrease  in  weight  of  Bartlett  pears 
during  ripening  through  transpiration  losses  of  moisture  are  available 
through  the  Cooperative  Cannery  at  San  Jose,  California.* 

During  the  1922  season  about  seven  tons  of  pears  were  handled. 
As  deliveries  of  fruit  were  made,  samples  of  25  pounds  were  removed. 
Each  sample  was  placed  two  layers  deep  in  a  lug  box.  The  boxes 
were  piled  nine  high,  with  space  between  each  stack,  in  a  sample  room 
having  ample  ventilation.  The  average  period  for  ripening  was  nine 
days  from  the  time  of  harvest.  The  loss  from  rot  was  almost  nil.  The 
decrease  in  weight  through  loss  by  transpiration  during  the  nine  days 
was  5.23  per  cent  or  about  104  pounds  per  ton. 


*  Furnished  through  the  courtesy  of  Dr.  T.  D.  Stewart,  Dept.  of  Chemistry, 
University  of  California. 


28 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 


The  authors  found  that  the  actual  moisture  loss,  however,  varied 
with  the  variety  and  the  stage  of  maturity  when  harvested,  as  shown 
by  the  data  in  table  9.  Fruit  of  each  picking  was  chosen  at  random 
immediately  after  harvest  and  placed  at  room  temperature,  having  a 
relative  humidity  of  about  55  per  cent.  Samples  averaging  1000  kilo- 
grams were  employed. 

TABLE  9 
Percentage  Loss  of  Moisture  from  Pears  during  a  Eipening  Period  of 
Twenty  Days  (1921) 


Variety 

Picking 

Date  of 
picking 

Per  cent 

moisture 

lost 

Hardy      

1st 

2nd 

Aug.  18 
Aug.  29 
Sept.    7 
Sept.  17 
Aug.  18 
Aug.  29 
Sept.    7 
Aug.  18 
Aug.  29 
Sept.    7 
Sept.  17 

13.7 

it 

12.9 

tt 

3rd 

12.8* 

n 

4th 

10.5 

Bosc               

1st 

12.3 

u 

2nd 

11.6 

It 

3rd 

9.1* 

Comice          

1st 

11.4 

tt 

2nd 

9.7 

n 

3rd 

9.2 

n 

4th 

7.2* 

Most  satisfactory  picking  for  storage. 


Of  the  three  varieties  tested,  the  Hardy  lost  the  largest  percentage 
of  moisture  and  the  Comice  the  least.  The  earliest  pickings  of  each 
variety  lost  the  greatest  quantities  of  moisture,  and  the  later  pickings 
least. 

Storage  for  Canning. — In  canning  the  pear  crop  it  is  often  of  value 
to  place  a  portion  in  cold  storage,  during  the  peak  period  to  lessen 
possible  spoilage  and  to  enable  peaches  and  other  more  perishable 
products  to  be  canned  first.  The  retention  of  pears  for  a  certain 
period  of  time  in  cold  storage  does  not  lower  their  quality  for  canning 
purposes. 

The  Bartlett,  if  properly  picked,  has  an  optimum  date,  not  earlier 
than  October  15  when  stored  at  30°  F.,  and  it  appears  that  a  portion 
of  the  crop  could  be  held  in  canning  condition  until  the  apricots, 
plums,  and  peaches  had  been  canned.  Magness17  found  that  storing 
the  Bartlett  for  optimum  periods  of  time  did  not  injure  its  quality 
for  canning. 


Bulletin  377]  THe  COLD  STORAGE  OF  PEARS  29 


VARIETAL   BEHAVIOR    IN    COLD    STORAGE 

The  data  concerning  the  behavior  of  varieties  of  pears  in  cold 
storage,  obtained  during  the  seasons  of  1918  to  1923,  inclusive,  are 
presented  in  table  10.  The  varieties  are  described  in  the  order  of  their 
optimum  storage  dates,  those  with  the  latest  dates  being  described  first. 

1.  Doyenne  d 'Alencon 

The  Alencon  was  obtained  from  Niles  and  from  Davis  for  two 
seasons.  Its  average  picking  date  was  September  28.  The  excessive 
wilt,  and  the  fact  that  the  fruit  did  not  ripen  when  removed  from 
storage  at  the  beginning  of  the  season,  during  the  first  season's 
observation,  indicate  that  this  variety  was  picked  too  early.  The  fruit 
was  picked  later  during  the  second  season  (October  17)  and  kept  to  a 
late  date.  The  quality  of  the  Alencon  was  low,  the  fruit  being  coarse 
and  flavorless. 

Behavior  at  32°  F. — The  quality,  poor  at  first,  became  fairly  good 
after  three  months'  storage.  Until  that  time  the  fruit  did  not  ripen 
when  removed  from  storage.  The  fruit,  prior  to  January  2,  was  dry ; 
after  that  date  a  little  juice  was  present.  The  optimum  and  maximum 
date  for  the  two  seasons  of  1921  and  1922  was  May  1,  or  215  days 
after  harvest.  The  quality,  up  until  May  1,  was  as  good  as  ever 
attained  but  thereafter  failure  rapidly  resulted  from  mold.  Hence  the 
optimum  and  maximum  storage  periods  were  made  to  coincide. 

Cause  of  Failure. — Failure  in  storage  of  early  picked  fruit  resulted 
from  wilt.  Wilt  determined  the  maximum  date  of  storage.  Fruit  late 
picked  was  attacked  by  Penicillium. 

2.  Lawrence 

This  variety  was  harvested  at  Niles  and  was  stored  at  32°  F.  during 
two  seasons.  The  average  picking  date  was  September  21.  The  fruit 
was  of  medium  size,  uniform  in  shape,  and  of  superior  quality.  It, 
however,  did  not  color  up  well  when  ripe,  remaining  greenish  or 
becoming  only  a  pale  straw  color.  It  was  one  of  the  best  varieties  for 
retention  in  cold  storage,  and  appeared  desirable  for  the  home  garden. 
For  a  late  shipping  or  storage  pear  it  also  appeared  worthy  of  trial  in 
California, 


30 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION 


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THE    COLD    STORAGE    OF   PEARS 


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32  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Behavior  at  32°  F. — At  32°  F.  the  Lawrence  kept  remarkably  well, 
retaining  its  good  qualities  unimpaired  until  April  11,  203  days  after 
harvest.  The  maximum  storage  date,  June  1,  was  more  than  seven 
months  after  harvest. 

3.  P.  Barry 

The  P.  Barry  was  obtained  from  Niles  for  two  seasons  with  an 
average  picking  date  of  September  18.  The  fruit  was  packed  loosely 
in  boxes.     One  portion  was  stored  at  32°  F.  and  the  other  at  36°  F. 

In  cold  storage  the  fruit  of  this  variety  retained  its  flavor  and 
melting,  buttery,  juicy  texture  long  after  most  other  pears  had  lost 
these  qualities.  It  also  had  an  optimum  storage  period  about  six 
months  in  length. 

Of  the  marketable  pears  of  good  quality,  it  ranked  second  to  the 
Lawrence  as  a  long  keeper.  The  fruit  ripened  evenly  in  storage.  It 
has  been  recommended  as  a  good  shipper  and  keeper  by  several 
authorities,2' 3  and  is  the  best  of  the  B.  S.  Fox  creations. 

The  P.  Barry  probably  was  a  trifle  immature  when  harvested  in 
1921,  as  evidenced  by  the  delay  in  ripening  without  storage.  The 
marked  acidity  noted  at  first  and  the  slight  amount  of  shriveling 
occurring  when  ripened  late  in  the  storage  season,  were  perhaps 
further  evidences  of  premature  picking. 

Behavior  at  32°  F. — At  32°  F.  the  optimum  storage  date  of  the 
P.  Barry  was  March  22,  or  185  days  after  harvest.  The  maximum 
date  was  May  20.  Without  storage  the  P.  Barry  required  twenty-four 
days  to  ripen  and  kept  fourteen  days  more  before  becoming  valueless. 
The  first  removal  at  32°  F.  was  inferior  in  quality  to  later  removals. 
The  intensity  of  the  acid  flavor  diminished  during  the  season  and  the 
sweetness  increased.  The  combination  of  acid  and  sugar  was  improved 
by  storage  at  32°  F. 

Behavior  at  36°  F.—At  36°  F.  the  optimum  date  was  February  20 
and  the  fruit  was  of  excellent  flavor.  The  quality  from  this  date  on, 
however,  was  inferior  to  that  of  the  fruit  held  at  32°  F.  At  36°  F. 
the  flavor  was  less  acid  than  at  32°  F.  The  maximum  date,  as  deter- 
mined by  the  poorer  flavor  and  softer  texture,  was  April  1.  Never- 
theless, its  quality  remained  good.  The  fruit,  however,  was  too  soft  to 
handle  successfully. 

Cause  of  Failure. — Failure  in  storage  resulted  from  Penicillium. 
There  was  no  scald  or  wilt  noticeable  in  storage.  On  removal  from 
storage,  failure  resulted  by  the  tissues  becoming  soft  and  the  surface 
somewhat  wrinkled. 


Bulletin  377]  THE  C0LD  storage  OF  PEARS  33 


4.    FORELLE 

The  Forelle  was  received  from  Davis  and  Niles  and  was  observed 
during  four  seasons.    The  average  date  of  harvest  was  September  16. 

This  variety  kept  better  at  36°  F.  This,  however,  might  not  have 
been  the  case  had  it  been  picked  more  mature.  Although  of  attractive 
appearance  and  sweet  flavor,  the  variety  was  surpassed  in  quality  of 
flesh  and  texture  among  other  long-keeping  varieties  by  "Winter  Nelis. 

In  Germany  it  is  a  favorite,  widely  planted  variety.13  Reimer25 
states  that  it  is  more  susceptible  to  blight  than  any  other  variety. 

Behavior  at  32°  F. — At  32°  F.  the  Forelle  was  one  of  the  longest 
keepers.  The  optimum  date  averaged  March  15,  the  maximum  date 
was  May  17. 

The  quality  developed,  when  stored  at  32°  F.,  was  good.  The 
texture  was  crisp  and  the  juiciness  medium.  On  removal  from  storage 
early  in  the  season,  the  Forelle  was  tough  and  did  not  ripen.  After 
two  months'  storage  the  fruit  ripened  fairly  well,  being  at  its  best 
after  January  1. 

Behavior  at  36°  F. — At  36°  F.  the  Forelle  attained  a  better  quality 
than  at  32°  F.  The  texture  was  not  so  coarse.  It  ripened  on  removal 
from  storage  one  month  earlier  than  at  32°  F.  The  removal  that  was 
made  the  first  week  in  October  ripened  in  good  condition.  During 
the  season  of  1921-22  the  end  of  the  optimum  period  was  February  20, 
ten  days  later  than  at  32°  F.    The  maximum  was  about  May  1. 

Cause  of  Failure. — Failure  after  removal  from  storage  was  caused 
by  internal  breakdown  and  wilt.  Failure  in  storage  resulted  from 
scald  and  Penicillium. 

5.  Columbia 

The  Columbia  was  obtained  during  the  1921-22  season  from  the 
Santa  Clara  Valley,  and  was  picked  on  September  18.  One  box  of 
carefully  wrapped  and  packed  fruit  was  stored  at  32°  F. 

This  pear,  of  varieties  under  observation,  was  one  of  the  more 
desirable  for  storage.  None  of  the  other  varieties  were  so  free  from 
mold  or  rot.  The  Lawrence,  Dearborn  Seedling,  and  P.  Barry  retained 
their  good  flavor  longer  than  the  Columbia,  but  were  more  perishable 
when  ripe.  With  the  exception  of  the  Block  "18,"  the  Columbia 
remained  in  a  marketable  condition  for  a  longer  period  after  removal 
from  storage  than  any  other  variety  under  observation  during  1921-22. 
At  the  optimum  date,  five  days  were  required  for  ripening  and  sixteen 
days  more  for  failure  to  occur. 


34  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

The  dark  colored,  rather  coarse  flesh  and  abundance  of  grit  cells, 
on  the  other  hand,  were  undesirable  characteristics.  Another  undesir- 
able feature  was  the  non-uniformity  of  ripening  after  removal  from 
storage.  This  was  more  noticeable  in  the  earlier  than  in  the  later 
removals.  One  to  two  weeks'  difference  in  the  time  of  ripening  was 
noted  in  pears  removed  from  storage  at  the  same  time.  This  marked 
variation  was  not  observed  in  any  other  variety. 

Behavior  at  32°  F. — At  this  temperature  the  variety  kept  excep- 
tionally well.  The  flavor  and  quality  of  the  flesh  improved  in  storage 
and  on  March  1  was  very  good.  In  the  removal  made  on  March  27  the 
flavor  was  still  rich,  but  the  fruit  had  become  drier  and  slightly 
astringent. 

The  optimum  date,  determined  by  the  loss  of  its  highest  quality, 
was  March  15,  or  178  days  after  the  fruit  had  been  picked.  The 
maximum  date  was  April  1.  The  fruit  appeared  normal  from  the 
outside,  but  was  found  to  have  suffered  severely  from  internal  break- 
down. Hence  poor  fruit  might  easily  be  placed  on  the  market  and 
appear  in  prime  condition  to  the  eye. 

Cause  of  Failure. — Failure  after  removal  resulted  from  drying  of 
tissues,  causing  them  to  become  mealy.  No  mold  or  scald  developed 
in  storage  or  after  removal. 

6.  Block  "18" 

The  Block  "18"  was  obtained  from  Santa  Clara  during  the  season 
of  1921-22,  on  October  24.  The  fruit  was  received  wrapped,  in  a 
standard  pack,  and  was  stored  at  32°  F. 

The  variety  possesed  a  splendid  appearance.  It  had  a  smooth  skin, 
uniform  shape,  and  freedom  from  blemishes.  It  was  also  valuable  in 
that  it  developed  a  richer  flavor  than  other  pears  of  the  Oriental  type. 

The  defects  noted  were  coarse  flesh  and  numerous  grit  cells,  and 
as  a  result  it  was  not  so  promising  for  storage  as  several  other  varieties. 

Behavior  at  32°  F.— The  variety  kept  satisfactorily  at  32°  F.  The 
maximum  date,  April  15,  was  determined  by  the  quality  and  flavor, 
which  was  fairly  good,  but  below  that  of  previous  removals.  The 
external  appearance,  however,  was  still  good. 

The  optimum  storage  date,  March  10,  at  32°  F.  was  exceeded  only 
by  Lawrence,  Doyenne  d'Alencon,  Dearborn  Seedling,  P.  Barry,  and 
Columbia.  The  number  of  days  to  the  optimum  date,  however,  was 
only  133,  because  of  the  late  harvest  date  of  October  24.  The  fruit 
remained  marketable  for  three  weeks  after  removal  from  storage  on 
the  optimum  date. 


Bulletin  377]  THe  COLD  STORAGE  OF  PEARS  35 

Furthermore,  the  maximum  date,  while  late  in  the  season,  was  only 
169  days  after  harvest.  This  period  was  exceeded  in  number  of  days 
by  twenty-one  other  varieties. 

Type  of  Failure. — Failure  after  removal  from  storage  resulted 
from  internal  breakdown  and  rot  at  the  core.  No  scald  or  wilt 
occurred,  and  mold  only  in  a  few  instances. 

7.  Vicar  op  Winkpield 

The  Vicar  of  Winkfield  was  obtained  from  Niles  during  the  seasons 
of  1921-22  and  1922-23.  This  variety,  although  large  and  attractive, 
was  of  inferior  quality  and  was  of  value  primarily  for  culinary  pur- 
poses. The  Vicar  of  Winkfield  has  been  recommended1  as  a  variety 
for  distance  shipment. 

Behavior  at  32°  F. — At  32°  F.  observations  were  made  on  fruit 
harvested  September  29,  1923.  The  fruit  was  apparently  in  good  con- 
dition for  storage,  having  attained  full  size.  The  optimum  storage 
date  was  March  1,  153  days  after  harvest,  and  the  maximum  date 
June  10,  eight  months  after  harvest. 

Failure  in  storage  resulted  from  attacks  of  Penicillium,  accom- 
panied by  scald  and  breakdown. 

8.  Winter  Nelis 

Winter  Nelis  pears  were  obtained  from  Niles,  Santa  Clara,  Davis, 
and  Helendale.  The  dates  of  harvest  were  as  follows:  from  Niles, 
September  7;  from  Santa  Clara,  September  15;  from  Helendale, 
October  15;  from  Davis,  October  29.  The  average  harvest  date,  for 
five  seasons,  was  September  22. 

The  Winter  Nelis,  because  of  the  retention  of  its  good  flavor  and 
texture  in  storage  until  a  late  date,  was  a  valuable  variety  for  storage. 
Winter  Nelis  pears  picked  as  late  as  October  29  kept  in  the  best  con- 
dition. Those  from  Niles,  picked  on  September  7,  did  not  attain  such 
rich  flavor,  nor  were  they  so  buttery  as  the  later  picked  pears.  This 
indicated  the  advantage  of  permitting  Winter  Nelis  to  become  well 
matured  before  harvesting. 

Behavior  at  32°  F— At  32°  F.  the  Winter  Nelis  kept  well  and 
retained  a  quality  of  "very  good"  until  near  the  end  of  its  keeping 
period.  This  variety  was  one  of  the  longest  keeping  pears  at  this 
temperature.  It  remained  in  a  marketable  condition  for  sixteen  days 
when  removed  from  storage  on  the  optimum  date,  which  averaged 
about  March  1.    The  maximum  date  was  about  April  25. 


36  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT   STATION 

Behavior  at  36°  F. — x\t  this  temperature  the  Winter  Nelis  was  an 
excellent  keeper,  and  had  an  optimum  storage  date  of  March  1.  The 
Winter  Nelis  kept  three  weeks  longer  than  the  Easter  Beurre  at  this 
temperature. 

Cause  of  Failure. — At  36°  F.  failure  was  caused  by  mold  and  rot. 
At  32°  F.  less  mold  or  wilt  occurred. 

9.  Brettonneau 

This  variety  was  observed  only  during  the  season  of  1922-23.  The 
date  of  harvest  was  October  5.  The  Brettonneau  pears  were  large  in 
size.  The  quality  was  poor,  resembling  the  Pound  in  this  respect.  It 
never  became  suitable  for  eating  out  of  the  hand.  It  required  seventy- 
five  days  for  the  fruit  to  ripen  after  harvest,  at  room  temperature,  and 
thereafter  the  fruit  remained  marketable  for  ninety  days. 

Behavior  at  32°  F. — At  this  temperature  failure  resulted  from 
wilting.  At  the  optimum  date,  February  22,  the  fruit  remained  in 
good  condition  for  sixty  days  after  removal  from  storage.  The 
maximum  storage  date  was  June  15. 

10.  Emile  d'Heyst 

This  variety  was  obtained  from  Niles  during  the  season  of  1922-23. 
The  fruit  was  of  such  low  quality — below  even  the  Vicar  of  Wink- 
field — that  a  description  is  not  merited.  At  32°  F.,  February  20  was 
the  date  of  optimum  storage  and  May  1  the  date  of  maximum  storage. 

11.  Beurre  Diel 

The  Beurre  Diel  was  picked  at  Niles  on  September  3.  One  portion 
of  this  lot  was  stored  at  32°  F.  and  another  at  36°  F. 

Behavior  at  32°  F.—At  a  temperature  of  32°  F.  the  Beurre  Diel 
kept  satisfactorily.  Scald  was  first  noticed  on  the  more  exposed  fruit 
in  the  box  on  April  1.  The  fruit  was  gritty  early  in  the  season,  but 
this  was  less  noticeable  after  a  short  period  of  storage.  The  grittiness, 
however,  was  never  sufficiently  pronounced  to  be  serious.  During 
storage  a  quality  of  "very  good"  was  acquired.  The  flavor  was  sub- 
acid when  ripened  without  having  been  in  storage.  As  the  season 
progressed  and  subsequent  removals  of  the  fruit  were  made,  a  richer 
and  sweeter  flavor  was  noted.  The  fruit  was  very  juicy,  even  in  the 
last  removal.  Its  behavior  in  storage  was  good,  with  the  retention  of 
quality  and  juiciness. 


Bulletin  377]  THe  cold  STORAGE  OF  PEARS  37 

The  optimum  storage  date  was  February  20.  The  maximum  date, 
April  1,  was  210  days  after  harvest,  and  while  the  flavor  at  the  time 
was  "very  good,"  scald  had  developed. 

A  temperature  of  32°  F.  effectively  checked  ripening  and  prevented 
the  development  of  Penicillium  on  the  fruit  of  the  Beurre  Diel.  At 
36°  F.,  however,  infection  and  growth  by  molds  was  pronounced. 


-•'-■   km 

W      ^F 


Fig.  9. — Beurre  Diel,  showing  characteristic  type  of  failure 
occurring  at  36°  F. 

The  late  date  of  the  optimum  period  and  the  absence  of  wilt  or 
mold  at  32°  F.,  together  with  the  fact  that  its  appearance  remained 
excellent,  indicated  that  this  variety  might  be  desirable  for  storage. 

Behavior  at  36°  F. — The  color  developed  at  this  temperature  was 
unsatisfactory,  being  yellow  and  mottled  with  green.  The  fruit  was 
ripe  by  November  15.  Nevertheless,  removals  made  after  this  date 
attained  better  quality  than  those  made  earlier.  Scald,  noticed 
January  10,  marked  this  as  the  maximum  storage  date. 

Cause  of  Failure. — Failure  when  ripened  out  of  storage  was  in  the 
form  of  internal  breakdown.    Failure  in  storage  at  32°  F.  was  caused 


38  UNIVERSITY    OF    CALIFORNIA.- —EXPERIMENT    STATION 

by  scald.  At  36°  F.  failure  was  due  to  a  spotting  of  the  fruit  as 
illustrated  in  figure  9.  Some  scald  also  occurred  at  this  temperature, 
and  considerable  Penicillium  developed. 

12.  Dearborn  Seedling 

This  variety,  one  of  the  earliest  to  be  harvested  at  Niles,  was 
observed  during  two  seasons.  The  average  picking  date  was  August  6. 
The  fruit  was  nearly  ripe  when  harvested  and  was  stored  at  32°  F. 
The  fruits  of  this  variety,  although  small,  were  uniform  in  size,  shape, 
and  color,  attractive  in  appearance,  and  pleasing  to  eat.  The  quality 
was  delicate,  juicy  and  sweet.    Failure  resulted  from  stem  end  rot. 

Behavior  at  32°  F.—At  this  temperature  the  fruit  kept  remarkably 
long,  and  remained  in  good  condition  until  the  middle  of  February. 
The  quality  remained  nearly  unchanged  throughout  the  storage  season. 

13.  Japanese  (Pyrus  seroiina) 

This  species  of  pear  was  observed  during  the  season  of  1922-23. 
The  date  of  harvest  was  September  29.  The  pears  during  their 
optimum  period  of  storage  at  32°  F.  were  of  very  low  quality,  being 
similar  to  the  Kieffer  in  this  respect.  This  fruit  was  subject  to  attacks 
from  Penicillium  and  also  tended  to  wilt  after  long  storage. 

14.  Pound 

•  The  Pound  was  harvested  September  29,  and  observed  during  the 
season  1922-23.  At  32°  F.  the  fruit  kept  until  February  15,  when 
failure  resulted  from  the  appearance  of  scald.  The  Pound  was  one  of 
the  largest  pears,  and  also  one  of  the  lowest  in  quality.  It  was  not  a 
dessert  fruit  and  could  be  recommended  only  for  cooking  purposes. 

15.  Hugo 

The  Hugo  was  obtained  from  Niles.  It  was  picked  September  1. 
As  the  supply  was  limited  all  the  fruit  was  stored  at  32°  F. 

Behavior  at  32°  F.—At  32°  F.  the  Hugo  kept  better  than  the  Beurre 
d'Anjou.  The  maximum  date  for  the  former  was  March  20,  as  com- 
pared with  February  26  for  the  latter.  Hugo  kept  three  weeks  longer 
than  the  Beurre  d'Anjou.  The  maximum  date  was  determined  by  the 
fact  that  on  March  20,  the  Hugo  had  become  dry  and  mealy. 


Bulletin  377]  THe  cold  STORAGE  OP  PEARS  39 

The  Hugo  may  be  recommended  as  a  variety  suitable  for  storage. 
It  was  slightly  better  than  the  Beurre  d  'An jou  in  this  respect.  It  also 
possessed  a  richer  flavor  and  finer  texture,  and  when  ripened,  the 
bright  yellow  color  was  more  attractive  than  the  duller  yellow  of  the 
Beurre  d'Anjou. 

16.  Glout  Morceau 

Glout  Morceau  pears  were  received  from  Davis.  Niles,  and  Santa 
Clara.  The  average  date  of  picking  for  three  seasons  was  about 
September  15. 

The  Glout  Morceau  showed  promise  as  a  variety  for  storage  because 
of  its  firm  skin,  sweet  flavor,  long  keeping  qualities,  and  freedom  from 
mold  and  rot.    It  should  not  be  picked  too  immature. 

Thomas25  describes  this  variety  as  variable  but  excellent  when 
fully  grown.  The  tree  is  vigorous  and  productive,26  and  the  fruit  is 
fairly  good  for  shipping  and  is  in  demand  on  the  London  markets.1 

Behavior  at  32°  F. — Before  storage,  the  Glout  Morceau  did  not 
ripen  satisfactorily.  It  was  not  until  the  removals  of  October  and 
later  that  the  pear  became  pleasing  to  the  taste.  The  optimum  date 
was  February  6,  and  the  maximum  date  March  26.  On  certain  years 
those  from  Davis  did  not  ripen  well.  In  the  last  removal  they  became 
sweet,  but  some  scald  had  developed.  Each  lot  removed,  colored  up 
yellow  and  became  sweet.  The  flesh,  however,  remained  very  firm  and 
tough. 

Cause  of  Failure.— Failure  in  storage  was  mainly  from  wilt.  This 
indicated  that  the  fruit  from  the  interior  valley  was  too  green  when 
picked.  Internal  breakdown  occurred  in  the  pears  obtained  from  the 
coastal  sections  when  brought  out  of  cold  storage  and  ripened  at  room 
temperature. 

17.  Winter  Bartlett 

The  Winter  Bartlett  was  obtained  from  Niles  for  two  seasons.  It 
was  picked  on  September  12. 

Behavior  at  32°  F. — The  Winter  Bartlett  kept  satisfactorily  at 
32°  F.  except  when  picked  too  green.  In  such  a  condition  the  fruit 
wilted  at  an  early  date.  It  became  yellow  in  storage  and  reached  the 
end  of  the  optimum  storage  period  February  1.  The  maximum  date 
of  April  22  was  determined  by  scald  in  green  fruit  and  by  core  rot  or 
internal  breakdown  in  the  more  matured  pears.  In  spite  of  the  fact 
that  the  pear  became  wilted,  the  quality  and  flavor,  which  was  fairly 
good,  remained  the  same.  The  length  of  the  maximum  keeping  period 
was  222  days. 


40  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT   STATION 

Although  the  flavor  was  good,  the  unattractive  appearance  of  the 
fruit  because  of  wilt,  when  picked  immaturely,  lowered  its  market 
quality. 

18.  Urbaniste 

The  average  picking  date  for  this  variety,  during  the  seasons  of 
1921-22  and  1922-23  was  September  11. 

The  Urbaniste,  with  two  season's  observations,  ranked  high  as  a 
variety  suitable  for  storage.  In  general  characters  the  fruit  resembled 
the  Hugo.  At  32°  F.  the  average  optimum  date,  February  1,  and  the 
maximum  date,  April  1,  were  later  than  for  most  other  varieties.  In 
flavor  and  quality  it  was  superior  to  the  Beurre  d'Anjou,  which  it 
also  resembled.  Thomas25  noted  that  the  Urbaniste  in  unfavorable 
locations  had  only  fair  quality.  Weldon20  stated  that  it  possessed  only 
medium  quality  in  California.  This  statement  did  not  apply  to  the 
pears  of  fine  quality  obtained  from  Niles. 

Cause  of  Failure. — Slight  wilting  in  storage  was  in  evidence  toward 
the  end  of  the  storage  period.  The  flavor  remained  ' '  very  good ' '  and 
pleasing.  Failure  upon  removal  from  storage  was  due  to  internal 
breakdown. 

19.  Zoe 

The  Zoe  was  obtained  from  Niles.  The  date  of  picking  was  Sep- 
tember 1.  This  was  a  good  variety  but  without  special  merit  when 
compared  with  some  of  the  standard  varieties. 

Behavior  at  32°  F. — The  Zoe  was  slow  to  ripen  without  storage. 
It  held  up  from  ten  to  twelve  days  when  removed  from  storage,  on  the 
optimum  date,  January  15.  The  flavor  was  "sugar  sweet/'  during 
the  storage  period.  The  quality  remained  "good."  The  fruit  was 
very  juicy  at  first,  but  only  "medium  juicy"  at  the  maximum  date, 
March  15. 

Cause  of  Failure. — Failure  on  removal  from  storage  was  charac- 
terized by  wilt  and  drying  out  of  the  tissues.  Failure  in  storage  was 
caused  by  wilt. 

20.  Easter  Beurre 

The  Easter  Beurre  was  obtained  from  both  the  coastal  and  valley 
regions.  The  average  picking  date  for  the  six  seasons  was  Sep- 
tember 14. 

The  Easter  Beurre  was  a  good  keeping  variety  at  32°  F.  It  was 
inferior  in  quality  and  flavor,  however,  to  other  long-keeping  sorts 
such  as  Winter  Nelis  and  Lawrence. 


Bulletin  377]  TfIE  COld  STORAGE  OF  PEARS  41 

Behavior  at  32°  F. — The  Easter  Beurre  pears  under  observation  at 
32°  F.  were  slow  in  ripening.  Many  of  the  specimens  did  not  ripen. 
Only  those  specimens  that  were  most  mature,  ripened.  On  January  3, 
the  optimum  date,  they  ripened  in  ten  days  after  removal  and  spoiled 
ten  days  later.  They  kept  in  good  condition  at  this  temperature  until 
April  7. 

Behavior  at  36°  F. — At  36°  F.  the  maximum  storage  period  of  the 
Easter  Beurre  was  February  10.  This  date  was  160  days  after  the  fruit 
was  picked.  This  variety  proved  to  be  susceptible  to  Penicillium  mold 
at  36°  F.  The  fruit  became  ripe  in  storage  at  this  temperature  on 
January  20.  This  date  was  six  weeks  later  than  the  optimum  date  of 
the  Winter  Nelis  stored  at  36°  F.  When  removed  from  the  36°  F. 
room,  the  fruit  rapidly  decayed  through  the  growth  of  Penicillium. 
This  was  not  the  case  with  pears  taken  from  the  32°  F.  room. 

Cause  of  Failure. — Failure  at  36°  F.  was  caused  by  Penicillium. 
The  characteristic  method  of  failure  is  illustrated  in  figure  5.  After 
ripening  at  36°  F.  the  fruit  was  easily  attacked  by  mold.  This  accounts 
for  the  short  time  between  the  maximum  and  optimum  dates  at  36°  F. 
Pears  removed  from  storage  at  32°  F.  failed  from  internal  breakdown. 

21.  Doyenne  du  Comice 

Doyenne  du  Comice  pears  were  obtained  from  Santa  Clara  and 
Davis.  Six  seasons'  observations  were  made.  The  average  picking 
date  was  September  5. 

Behavior  at  32°  F. — The  average  optimum  storage  date  of  this  high 
quality  pear  was  January  3,  or  120  days  after  harvest.  The  maximum 
date  was  February  14,  or  five  months  in  storage. 

Behavior  at  36  F. — At  36°  F.  the  average  optimum  storage  date 
was  November  17,  or  67  days  after  harvest.  The  maximum  date  was 
December  16,  or  97  days  after  the  fruit  entered  storage. 

Cause  of  Failure. — Scald  and  rot  were  the  limiting  factors  in 
storage  at  both  32°  F.  and  36°  F.  See  pages  8  to.  10  for  further  dis- 
cussion of  the  Doyenne  du  Comice. 

22.  Kieffer 

The  Kieffer  was  obtained  from  Niles  and  Davis.  The  average  pick- 
ing date  was  August  24.    The  pears  were  stored  at  32°  F.  only. 

The  fruit  was  small  to  medium  in  size,  and  of  poor  quality.  In 
flavor  the  fruit  was  pungent  and  at  all  times  sub-acid.  In  color  it  was 
yellowish  green. 


42  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Behavior  at  32°  F. — The  average  optimum  and  maximum  storage 
dates  were  January  1  and  March  15,  respectively.  At  no  time  during 
the  storage  period  did  the  fruit  'become  suitable  for  eating  out  of 
hand,  nor  did  it  ever  approach  even  the  low  standard  of  quality 
recognized  for  this  variety.  The  best  stage  of  ripeness  appeared  in 
the  third  removal  from  storage,  the  fruit  becoming  fairly  good  in 
quality  about  November  23. 

23.  Beurre  d 'Anjou 

The  Beurre  d'Anjou  was  obtained  from  both  the  coastal  and 
interior  valley  sections  for  six  seasons.  The  average  harvest  date  was 
August  13,  which  proved  to  be,  in  most  seasons,  several  weeks  too  early. 

This  variety  may  be  recommended  because  of  its  popularity, 
appearance,  and  good  keeping  qualities.  It  is  free  from  fungous 
diseases  and  relatively  free  from  rot.  Thomas25  states  that  "the 
hardiness,  uniformity,  reliability,  excellence  and  long  keeping  qualities 
of  the  Beurre  d  'Anjou  render  it  one  of  the  most  valuable  of  all  pears. ' ' 

Behavior  at  32°  F. — The  flavor  and  quality  improved  in  storage 
and  were  best  about  November  1.  At  that  date  the  fruit  was  extremely 
juicy,  and  the  texture,  quality,  and  flavor  were  excellent.  The  flesh 
tended  to  become  a  little  grainy  towards  the  end  of  the  season. 

The  average  optimum  and  maximum  dates  at  32°  F.  were  Decem- 
ber 24  and  February  26,  133  and  197  days,  respectively,  from  the  time 
of  harvest. 

Behavior  at  36°  F. — At  this  temperature  the  variety  kept  remark- 
ably well.  The  quality  of  the  pears  kept  at  36°  F.  was  inferior  to  that 
of  the  pears  at  32°  F. ;  less  juice  was  present.  A  comparison  of  the 
effects  of  the  two  temperatures  showed  32°  F.  as  the  better. 

Cause  of  Failure. — The  Anjou  pears  were  not  subject  to  mold.  The 
characteristic  mode  of  failure  when  removed  from  storage  was  internal 
breakdown.  In  storage,  failure  was  characterized  by  a  rot  commenc- 
ing at  the  base  of  the  stem  where  it  joined  the  epidermis. 

24.  Beurre  Bosc 

The  Beurre  Bosc  was  obtained  from  Davis  and  the  Santa  Clara 
Valley,  and  was  observed  for  six  seasons.  The  average  picking  date 
was  August  28.    The  variety  was  stored  at  both  32°  F.  and  36°  F. 

The  Beurre  Bosc,  on  account  of  its  attractive  appearance  and  its 
retention  of  flavor,  was  a  good  variety  for  storage.  In  certain  seasons 
the  flesh  was  a  trifle  coarse,  an  objectionable  feature,  but  not  a 
characteristic  of  the  variety. 


Bulletin  377]  THe  COLD  STORAGE  OF  PEARS  43 

Behavior  at  32°  F. — At  this  temperature  the  optimum  date  was 
about  December  22 ;  the  maximum  storage  date  was  February  8. 

Behavior  at  36°  F. — At  36°  F.  the  more  mature  specimens  of 
Beurre  Bosc  kept  for  a  shorter  period  of  time  than  at  32°  F.  The 
quality  of  the  mature  Beurre  Bosc  pears  developed  at  36°  F.  was 
somewhat  inferior  to  that  developed  at  32°  F.  With  the  prematurely 
picked  Beurre  Bosc  pears,  however,  the  fruit  was  better  in  both 
respects  at  36°  F.  than  at  32°  F. 

Type  of  Failure. — The  type  of  failure  was  wilt  and  internal  break- 
down at  32°  F.,  and  scald  at  36°  F.  The  Beurre  Bosc  proved  to  be 
relatively  free  from  mold  in  storage.  See  pages  6  to  8  for  further 
discussion  of  the  Beurre  Bosc. 

25.  White  Doyenne 

The  White  Doyenne  was  obtained  from  Niles  for  three  seasons. 
The  average  picking  date  was  September  12.  This  variety  retained 
its  good  qualities  in  cold  storage  to  a  high  degree.  It  should  not  be 
harvested  when  too  green  or  too  ripe. 

Behavior  at  32°  F. — Upon  removal  from  storage  the  WThite 
Doyenne  attained  a  quality  of  "very  good,"  but  remained  so  only 
four  or  five  days  after  ripening.  It  then  became  dry  and  mealy.  The 
optimum  storage  date  was  December  1,  and  the  maximum  February  23. 

Cause  of  Failure. — In  storage  the  variety  was  attacked  by  mold. 
There  was  also  loss  from  wilting  and  internal  breakdown. 

26.  Dana  Hovey 

The  Dana  Hovey  was  obtained  from  Niles  for  four  seasons.  The 
average  date  of  harvest  was  September  14.  The  fruit  was  picked  and 
packed  loosely  in  the  box  without  being  wrapped. 

This  variety,  being  compartively  late  in  date  of  ripening  would, 
the  indications  were,  have  kept  better  if  picked  a  week  or  so  later. 
Evidence  of  premature  picking  was  the  slight  amount  of  wilting  that 
occurred  during  storage,  and  the  length  of  time — fourteen  days — it 
required  for  ripening  without  storage. 

Behavior  at  32°  F. — The  entire  lot  was  stored  at  32°  F.  The  length 
of  the  maximum  storage  extended  over  a  period  of  165  days,  and  the 
date  was  recorded  as  March  1. 

The  rich  flavor  and  high  quality  of  the  Dana  Hovey  was  impaired 
more  by  storage  than  was  the  case  with  many  other  varieties.  This 
was  the  chief  reason  for  placing  the  optimum  date  as  December.  At 
that  time  a  quality  of  ' '  best ' '  was  noted  for  the  last  time.     The  fruit 


44  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

was  very  juicy  but  became  slightly  drier  during  storage.  The  quality 
was  so  high  to  begin  with  that  although  impaired,  it  was  still  rich  and 
sweet  on  February  1.  The  variety  ranked  close  to  the  Seckel  pear  in 
quality.  Upon  removal  from  storage  at  the  optimum  date,  this  variety 
held  up  for  fourteen  days  in  good  condition. 

27.  Commerce 

The  Commerce  was  obtained  from  Santa  Clara  during  the  season 
of  1921-22.  The  date  of  picking  was  September  18.  One  box  of 
carefully  packed,  wrapped  fruit  was  received. 

The  Commerce  ranked  high  among  the  varieties  desirable  for 
storage,  and  retained  its  good  qualities.  "When  in  a  ripe  condition, 
its  flesh  and  delicate  skin  necessitated  care  in  handling.  Its  grittiness 
was  also  somewhat  objectionable. 

Behavior  at  32°  F. — This  variety  was  stored  only  at  32°  F.  It 
behaved  creditably  and  proved  to  be  one  of  the  better  keepers.  This 
was  remarkable  since  the  fruit  was  ripe  in  storage  by  January  15. 
It  was  apparently  in  nearly  the  same  condition  on  April  1  as  on  the 
former  date.  Before  being  stored  this  variety  ripened  in  thirteen  days 
and  was  valueless  six  days  later,  nineteen  days  in  all.  After  nearly 
three  months'  storage  at  the  optimum  date,  the  fruit  ripened  in  three 
days  and  became  valueless  thirteen  days  later,  sixteen  days  in  all. 
Storage  until  the  optimum  date,  therefore,  did  not  materially  shorten 
the  keeping  period  after  removal. 

Cause  of  Failure. — Failure  after  removal  was  occasioned  by 
internal  breaking  down  of  the  tissues. 

28.  Gr,vy  Winter 

This  variety  was  obtained  from  Niles  and  observed  during  two 
seasons.  The  average  date  of  harvest  was  September  12.  It  was  stored 
at  32°  F. 

Behavior  at  32°  F. — The  variety  kept  well  in  storage  until  Decem- 
ber 19,  98  days  after  harvest.  Failure  resulted  from  breakdown.  The 
fruit  was  round  and  completely  and  smoothly  russeted.  The  flesh  was 
delicate,  aromatic,  buttery,  and  melting. 

29.  Duchesse  d'Angouleme 

The  average  picking  date  for  the  Angouleme  from  both  Davis  and 
Niles  was  August  30,  The  varietal  behavior  was  observed  during  five 
seasons. 


Bulletin  377]  THe  cold  STORAGE  OF  PEARS  45 

Behavior  at  32  F. — At  this  temperature  there  was  little  difference 
in  the  length  of  time  that  the  pears  from  Davis  and  Niles  remained  in 
a  marketable  condition.  The  average  optimum  storage  date  was 
December  3 ;  the  maximum  date,  January  23.  Failure  resulted  from 
scald  about  February  1  in  both  cases. 

30.  Louise  Bonne  de  Jersey 

The  average  harvest  date  of  the  Louise  Bonne  de  Jersey  was  Sep- 
tember 9.  It  was  obtained  both  from  Davis  and  Niles,  The  deficiency 
in  this  variety  was  the  rather  short  period  of  time  the  fruit  remained 
in  a  marketable  condition  after  removal  from  storage.  Otherwise  this 
pear  was  commendable  for  storing  until  Christmas.  Thomas25  men- 
tioned the  fact  that  the  variety  is  exceedingly  productive. 

Behavior  at  32°  F. — The  fruit  of  this  variety  was  extremely  juicy 
at  first  but  became  drier  after  two  months'  storage  at  32°  F. 

Behavior  at  36°  F. — At  36°  F.  the  Louise  Bonne  de  Jersey  was  ripe 
in  storage  about  November  6. 

Cause  of  Failure. — This  variety  was  attacked  by  molds  in  storage, 
and  failed  from  wilt  and  rot.  Failure  after  removal  was  due  to 
internal  breakdown. 

31.  Winter  Seckel 

Winter  Seckel  was  received  from  the  Santa  Clara  Valley.  It  was 
picked  on  October  7  and  stored  at  32°  F. 

Behavior  at  32°  F. — The  Winter  Seckel  ripened  in  storage  within 
two  to  three  weeks.  Quite  remarkable  was  the  fact  that  it  remained 
thus  in  excellent  condition  until  January  1,  approximately  three 
months,  at  which  date  scalding  and  internal  breakdown  occurred 
simultaneously. 

Storage  for  three  weeks  seemed  to  improve  the  quality  somewhat, 
and  lengthened  by  four  days  the  period  of  time  for  which  it  might 
be  kept  when  removed  from  storage.  This  variety  kept  in  good  con- 
dition for  from  eight  to  twelve  days  after  removal  from  storage.  It 
reached  a  quality  designated  as  "very  good"  to  "best,"  and  a  flavor 
rich  and  spicy,  resembling  the  true  Seckel,  although  more  nearly 
approaching  the  flavor  of  the  Dana  Hovey. 

32.  Howell 

The  Howell  was  obtained  from  both  Davis  and  Niles  and  was 
observed  during  six  seasons.  The  average  harvest  date  was  August  20. 
The  chief  defect  of  the  Howell  variety  was  the  short  period  during 
which  it  retained  its  good  qualites  after  becoming  ripe. 


46  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

The  Howell  pears  from  the  interior  valley  matured  earlier  in  the 
orchard  than  those  from  the  coastal  section.  They  were  also  larger, 
juicier,  sweeter,  and  more  attractive  when  grown  in  the  warmer 
interior  valley.  They  did  not,  however,  keep  as  long  as  when  grown 
in  the  coastal  section.  The  trees  of  this  variety  wTere  free  from  insects 
and  diseases.    Weldon20  stated  that  it  was,  however,  subject  to  blight. 

Behavior  at  32°  F. — The  optimum  storage  date  was  November  15, 
and  the  maximum  date  was  December  9,  ah  average  of  102  days  after 
harvesting.  At  the  maximum  storage  date  the  quality  was  good, 
although  not  equal  to  the  quality  earlier  in  the  season. 

Behavior  at  36°  F. — At  this  temperature  the  Howell  pear  proved 
to  be  a  poor  keeper.  It  ripened  quickly  in  storage.  Upon  removal, 
both  the  Davis  and  Niles  pears  were  worthless  in  four  days  on  account 
of  internal  breakdown. 

Cause  of  Failure. — During  the  season  of  1921-22,  the  pears  from 
Davis  failed  because  of  internal  breakdown,  perhaps  because  of  over- 
ripeness  at  the  time  of  harvest.  Those  from  Niles  failed  from  the  same 
cause.  The  fruit  would,  from  surface  appearance,  apparently  be  in 
prime  condition,  while  inspection  of  the  interior  would  disclose 
internal  breakdown  in  an  advanced  stage.  Late  in  the  storage  period, 
round  spots  resembling  a  dry  rot  appeared  on  the  fruit.  The  Howell 
was  subject  to  the  attacks  of  blue  mold  and  was  also  injured  by 
pressure  in  the  box  when  approaching  ripeness.  At  36°  F.  the  Howell 
from  Niles  was  severely  attacked  by  blue  mold.  Scald  also  appeared 
to  a  considerable  degree  upon  this  variety. 

33.  Onondaga 

The  Onondaga  was  obtained  from  Niles  for  two  seasons.  The  average 
date  of  picking  was  September  1.  Two  boxes  of  this  variety,  were 
available  for  storage.     One  was  stored  at  32°  F.,  the  other  at  36°  F. 

The  shortness  of  the  optimum  storage  period,  and  the  susceptibility 
to  molds,  especially  when  bruised,  placed  the  Onondaga  as  one  of  the 
poorer  keepers.  It  was  inferior  in  quality  and  flavor,  becoming  some- 
what astringent.  Thomas25  also  noted  that  this  pear  was  sometimes 
astringent.    Weldon20  claimed  that  it  was  of  no  value  in  California. 

Behavior  at  32°  F. — The  behavior  of  this  variety  in  storage  was 
unfavorable.  The  optimum  date  at  32°  F.  was  November  15,  and  the 
maximum  date  December  20.  The  pears  were  subject  to  mold  and 
decay  in  storage.  Furthermore,  mold  always  caused  failure  after 
removal  from  storage.  The  fruit  was  as  susceptible  to  attack  by  mold 
as  any  of  the  varieties. 


Bulletin  377]  The  cold  STORAGE  OF  PEARS  47 

Behavior  at  36°  F. — The  optimum  date  at  36°  F.  was  November  1, 
59  days  from  the  date  of  picking.    The  maximum  date  was  February  1. 

34.  Beurre  Hardy 

The  Beurre  Hardy  pears  were  obtained  from  Davis  and  Santa 
Clara.  The  average  date  of  harvest  for  the  six  seasons  was  August  21. 
The  fruit,  however,  was  somewhat  immature  for  best  keeping  quality 
in  cold  storage.    A  portion  was  stored  at  32°  F.,  and  another  at  36°  F. 

Behavior  at  32°  F. — At  32°  F.  the  Beurre  Hardy  retained  its  good 
qualities  for  a  considerable  period  of  time.  The  average  optimum 
storage  date  was  November  9.  The  average  maximum  storage  date 
was  December  31. 

Behavior  at  36°  F. — At  36°  F.  the  keeping  period  of  the  Beurre 
Hardy  was  short.  The  average  optimum  keeping  date  was  October  20. 
The  maximum  storage  date  was  December  20.  See  pages  11  and  12 
for  further  discussion  of  the  Hardy. 

35.  Seckel 

The  Seckel  was  obtained  from  both  Davis  and  Niles.  The  average 
harvest  date  for  four  years  was  August  18. 

The  quality  and  flavor  of  this  pear  were  impaired  by  cold  storage. 
The  pears  being  in  a  semi-ripe  condition  soon  passed  their  best  stage 
in  storage. 

Behavior  at  32°  F. — A  marked  difference  was  noted  between  the 
behavior  of  Seckel  pears  exposed  to  the  relatively  dry  air  of  the 
storage  room  and  those  that  were  well  covered.  In  the  case  of  the 
former,  wilting  occurred  as  early  as  December  1,  while  those  well 
protected  were  in  good  condition  three  weeks  later.  The  average 
optimum  storage  date  was  November  1,  and  the  maximum  date 
December  19. 

36.  Beurre  Clairgeau 

The  Beurre  Clairgeau  pears  used  in  the  experiment  were  obtained 
from  Davis,  Niles,  and  Santa  Clara.  The  average  date  of  harvest 
during  six  years'  observation  was  August  15.  All  were  stored  at  32°  F. 

There  are  so  many  good  varieties  of  pears  that  it  seemed  undesir- 
able to  search  for  any  special  merits  in  such  a  poor  variety  as  the 
Beurre  Clairgeau.     Sinclair2^  recommended  it  for  cooking. 

Behavior  at  32°  F. — In  the  observations  made,  the  quality  of  the 
Clairgeaus  from  Santa  Clara  was  noted  as  "very  good"  for  the 
variety,    when    ripened    without    storage;    as    "good"    in    the    first 


48  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

removals,  after  being  kept  in  storage  for  from  eight  to  fourteen  weeks. 
After  this  period  the  pear  was  nearly  worthless  as  far  as  marketability 
was  concerned.  In  the  lot  from  Niles  the  quality  was  fairly  good,  but 
after  six  weeks'  storage  it  became  only  fair  and  later  quite  poor.  The 
lot  from  Davis  kept  longer  and  better,  bringing  the  average  maximum 
date  to  January  23. 

Cause  of  Failure. — The  Clairgeau  variety  kept  satisfactorily  in 
storage  and  no  defects  were  noticed  until  scald  suddenly  made  its 
appearance  about  January  10,  and  the  entire  box  rapidly  became 
affected. 

37.  Flemish  Beauty 

The  Flemish  Beauty  was  observed  four  seasons.  The  average 
harvest  date  in  the  interior  valley  was  August  6 ;  in  the  coastal  section 
about  September  1. 

The  color  was  yellow,  the  skin  was  heavily  russetted,  the  size  was 
medium  large,  and  the  flavor  was  sweet  and  aromatic. 

Behavior  at  32°  F. — The  optimum  storage  period  of  the  Flemish 
Beauty  was  about  October  29 ;  the  maximum  December  29.  After  the 
optimum  storage  period  the  flavor  became  less  pronounced  and  the 
quality  dropped  from  "very  good"  to  "good"  and  later  to  only 
"fairly  good."  The  fruit  that  remained  in  good  condition  was  ripe 
in  storage  by  January  1,  and  broke  down  rapidly  after  removal.  The 
amount  of  juice  decreased  rapidly  during  storage. 

38.  Bartlett 

The  behavior  of  the  Bartlett  pear  in  cold  storage  was  observed  for 
six  seasons.  Fruit  was  obtained  from  various  sections  of  the  state. 
From  three  to  five  pickings  were  made  each  season.  The  average  pick- 
ing date  was  August  24. 

The  Bartlett  was  not  a  suitable  variety  for  long  storage.  It  was 
subject  to  scald  and  could  not  be  recommended  as  a  variety  to  be  kept 
for  the  holiday  trade.  There  were  many  other  varieties  that  were  less 
perishable  under  storage  conditions  than  the  Bartlett. 

Behavior  at  32°  F. — The  average  optimum  storage  date  was 
October  29,  or  66  days  after  harvest.  The  maximum  storage  date  was 
December  18,  116  days  after  harvest. 

Behavior  at  36°  F. — At  this  temperature  the  average  optimum 
storage  date  was  October  11,  or  46  days  after  harvest.  The  maximum 
storage  date  was  October  24. 


Bulletin  377]  the  cold  STORAGE  OF  PEARS  49 

Cause  of  Failure. — At  both  32°  F.  and  36°  F.,  the  fruit  became  ripe 
in  storage;  scald  rapidly  made  its  appearance  and  soon  involved  the 
entire  lot.  The  effect  of  various  factors  upon  the  keeping  quality  and 
upon  scald  is  described  elsewhere  in  this  publication. 


Pig.  10— Bartlett  (left),  Chadbourne  (right),  harvested  August  9,  1923, 
at  the  optimum  picking  date  for  both. 

39.  Chadbourne 

This  variety,  obtained  during  the  seasons  of  1922-23  and  1923-24 
at  Niles,  was  stored  at  32°  F.  The  Chadbourne  was  discovered  on  the 
J.  R.  Chadbourne  ranch  at  Suisun,  California,  and  was  propagated 
by  George  C.  Roeding  at  Niles.  It  appeared  to  be  a  bud  variation  of 
the  Bartlett.  It  was  thought  to  be  earlier  than  the  Bartlett,  as  it 
attained  Bartlett  size  two  weeks  in  advance  of  that  variety.  When  at 
the  proper  maturity  for  harvest,  however,  the  Chadbourne  was  a  larger 
and  somewhat  rougher  pear  than  the  Bartlett  (fig.  10).  This  would 
lower  its  value  as  a  variety  suitable  for  canning. 

Behavior  at  32°  F. — During  the  season  1922-23,  the  first  picking 
was  made  July  12,  and  the  second  July  22.  For  the  fruit  thus 
harvested  the  average  optimum  date  was  September  30  and  the 
maximum  storage  date  about  October  8.  The  second  picking  was 
superior  in  color,  texture,  and  flavor.  The  behavior  and  appearance 
of  both,  however,  indicated  immaturity  at  the  time  of  harvest. 


50  UNIVERSITY   OF    CALIFORNIA—EXPERIMENT   STATION 

During  the  season  of  1923-24  the  fruit  was  harvested  later.  The 
picking  dates  were  July  24  and  31,  and  August  9.  The  Chadbourne 
harvested  July  24  were  fully  as  large  in  size  as  the  Bartlett  harvested 
two  weeks  later. 

Behavior  at  36°  F. — During  the  season  1923-24  the  fruit  harvested 
August  9  kept  later  and  better  than  that  harvested  earlier.  The  first 
picking  tended  to  wilt  slightly  in  storage;  scald  occurred  about 
December  20.  The  second  picking  showed  signs  of  scald  by  January  8, 
while  the  third  picking  was  yellow  ripe  and  still  in  good  condition  on 
that  date.  The  results  of  the  experiment  indicated  that  although  the 
Chadbourne  attained  a  size  equal  to  that  of  the  Bartlett  fully  two 
weeks  in  advance  it  should  be  harvested  at  approximately  the  same 
time  as  the  Bartlett.  When  harvested  at  that  stage  of  maturity,  the 
Chadbourne,  in  size,  quality  and  color,  surpassed  the  Bartlett  grown 
in  the  same  region.  An  excellent  feature  of  the  Chadbourne  was  that 
the  fruit,  although  it  frequently  attained  considerable  size,  did  not 
drop  prematurely  from  the  tree. 

40.  Le  Conte 

The  average  picking  date  of  this  variety  for  four  years  was 
August  13.  The  variety  was  stored  at  32°  F.  It  has  little  commercial 
value  in  this  state.  Its  principal  value  lies  in  the  fact  that  it  is 
resistant  to  blight,  especially  in  the  warmer  sections  east  of  the  Rockies. 

Behavior  at  32°  F. — Le  Conte  was  found  to  keep  only  a  short  time 
in  storage,  the  tissues  turning  brown  and  the  fruit  becoming  valueless 
generally  as  early  as  November  26. 

41.  Clapp  Favorite 

This  variety  was  observed  for  four  seasons.  The  average  picking 
date  was  July  14.  This  variety  was  rather  perishable  for  retention  in 
storage.  It  was,  however,  a  pear  of  high  quality  and  was  excellent  as 
a  dessert  fruit  when  not  stored.  It  was  made  attractive  by  its  red 
blush,  large  size,  and  good  form. 

Behavior  at  32°  F.—At  32°  F.  the  Clapp  Favorite  had  an  optimum 
storage  date  of  October  2,  and  a  maximum  storage  date  of  November  1. 
Failure  in  storage  resulted  from  rot,  wilt,  scald,  Penicillium,  and 
breakdown. 

42.  Idaho 

One  year  of  observation  showed  this  variety  to  be  a  short  keeper. 
The  fruit,  although  large  and  resembling  Duchesse  dAngouleme  in 
character  of  flesh  and  flavor,  was  typically  apple-shaped,  with  an 


Bulletin  377]  the  cold  STORAGE  OF  PEARS  51 

irregular  surface.  Its  inferior  quality  when  compared  with  many 
other  varieties  and  its  short  keeping  period  would  probably  prevent 
it  from  becoming  a  commercial  possibilty  in  California. 

43.  Bloodgood 

Five  years'  observation  of  the  Bloodgood  obtained  from  Davis 
showed  an  average  picking  date  of  July  18. 

At  a  temperature  of  32°  F.  the  average  optimum  date  was  Sep- 
tember 7,  while  the  maximum  was  October  15,  or  85  days  after  harvest. 

Storage  at  36°  F.  was  unsatisfactory,  because  of  the  early  date  at 
which  the  fruit  failed. 

Failure  in  storage  resulted  from  wilt  in  immature  pickings,  and 
rot  and  mold  in  pickings  made  at  a  more  matured  stage. 

Bloodgood  has  little  value  as  a  commercial  fruit  because  of  its 
small  size  and  poor  quality. 

44.  Other  Varieties 

The  varieties  Gifford,  Madeleine,  Lawson,  Lincoln,  Margaret,  Fame, 
Col.  Wilder,  Rossenay,  B.  S.  Fox,  and  Colorado  Seedless,  as  shown  in 
table  10,  were  of  inferior  keeping  quality. 


SUMMARY 

A.  Causes  of.  the  Spoiling  of  Pears  in  Storage 

1.  Scald,  manifested  by  a  darkening  of  the  epidermis,  occurred 
with  certain  varieties  of  pears  when  stored  at  low  temperatures, 
namely  45°,  36°,  32°,  and  30°  F.  Fruit  not  placed  in  cold  storage 
but  ripened  at  room  temperature  did  not  develop  scald. 

2.  Blue  mold  (Penicillhim  sps.)  was  the  principal  mold  making 
appreciable  growth  at  a  temperature  of  32°  F.  It  made  more  rapid 
development  at  36°  and  45°  F. 

3.  Internal  breakdown  or  softening  of  the  tissues  was  noted  in 
many  varieties  at  all  temperatures  used  (30°,  32°,  36°,  45°  F.),  and 
also  at  room  temperature  (65°  F.). 

4.  Wilting  occurred  with  all  varieties  harvested  in  a  very  green 
stage  of  maturity  and  occasionally  with  more  matured  fruit.  Wilting 
was  more  common  at  32°  F.  and  30°  F.  than  at  higher  temperatures 
for  the  same  variety. 

5.  Ammonia  fumes,  when  anhydrous  ammonia  is  employed  to 
obtain  refrigeration,  may  sometimes  unavoidably  gain  entrance  to 


52  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

storage  rooms.  When  pears  were  exposed  to  ammonia  fumes  the  cells 
immediately  adjacent  to  the  lenticel-like  openings  of  the  epidermis 
became  black  in  color.  Upon  prolonged  exposure,  the  depth  of 
penetration  and  area  of  surface  blackened  increased. 

B.  Summary  of  Observations.    Factors  Affecting  Rate  of 
Spoiling  in  Storage 

1.  Temperature. 

Pears  kept  better  and  longer  at  30°  F.  to  32°  F.  than  at  36°  F.  to 
45°  F.  when  harvested  at  the  proper  stage  of  maturity.  The  average 
maximum  keeping  period  of  the  four  varieties.  Beurre  d'Anjou, 
Doyenne  du  Cornice,  Beurre  Bosc,  and  Howell,  at  30°  F.,  was  143 
days;  at  45°  F.,  the  average  maximum  keeping  period  was  37  days. 

When  fruit  was  picked  in  too  green  a  stage  of  maturity  it  generally 
kept  better  and  attained  a  more  desirable  quality  when  stored  at 
36°  F.  than  at  lower  temperatures.  This  was  particularly  true  With 
Beurre  Bosc,  Forelle,  Gray  Winter,  and  Vicar  of  Winkfield. 

Pears  held  at  36°  F.  scalded  more  severely  and  at  an  earlier  date 
than  at  30°  or  32°  F.  At  45°  F.,  decay  generally  resulted  before  scald 
developed. 

The  blue  mold  (Penicillium  sps.)  occurred  upon  certain  varieties 
of  pears  at  all  of  the  storage  temperatures  utilized.  The  lower 
temperatures,  however,  delayed  its  appearance  and  retarded  its 
growth,  as  for  example,  the  Easter  Beurre  at  36°  F.  developed  blue 
mold  by  February  10,  but  at  32°  F.  developed  no  mold  as  late  as  May  1. 

2.  Degree  of  maturity  at  time  of  harvest. 

The  average  maximum  storage  period  of  the  Beurre  Bosc,  Doyenne 
du  Cornice,  and  Beurre  Hardy,  picked  during  the  height  of  the  com- 
mercial harvest,  was  141  days  at  32°  F.  When  harvested  about  two 
weeks  later  at  a  somewhat  more  advanced  stage  of  maturity,  they  kept 
for  158  days  or  nearly  two  and  one-half  weeks  longer,  and  suffered 
less  from  wilt  and  scald  in  storage. 

Overripe  fruit,  however,  was  more  objectionable  than  underripe 
fruit  and  deteriorated  with  even  greater  rapidity  in  cold  storage  than 
immature  pears. 

Overripe  fruit  was  more  susceptible  to  the  attacks  of  blue  mold 
than  prematurely  picked  fruit. 

The  immature  fruit  generally  scalded  sooner  after  harvest  than  did 
the  properly  matured  fruit;  overripe  fruit,  however,  scalded  more 
rapidly  and  severely  than  either. 


Bulletin  377]  THE  C0L1>  storage  OF  PEARS  53 

Pears  picked  in  an  immature  condition  were  more  susceptible  to 
ammonia  fumes  than  when  well  matured. 

3.  Variety. 

Susceptibility  to  scald  of  the  varieties  studied  was  found  to  be  in 
about  the  following  order :  Bartlett,  Louise  Bonne  de  Jersey,  Beurre 
Clairgeau,  Duchesse  de  Bordeaux,  Vicar  of  Winkfield,  Pound,  Beurre 
Hardy.  Beurre  Hardy  was  the  least  susceptible  but  was  somewhat 
variable  in  this  respect. 

The  varieties  which  exhibited  considerable  resistance  to  the  develop- 
ment of  scald  were :  Easter  Beurre,  Forelle,  P.  Barry,  and  Beurre 
d  'Anjou. 

Certain  varietal  suceptibility  in  storage  to  blue  mold  (Penicillium 
sps.)  was  indicated. 

The  Columbia,  Doyenne  d'Alencon,  and  Seckel,  of  the  varieties 
studied,  were  relatively  immune  to  the  blue  mold. 

The  varieties  relatively  susceptible  were  as  follows:  Onondaga, 
Flemish  Beauty,  Beurre  Diel,  Easter  Beurre,  Urbaniste,  and  Howell. 

4.  Care  in  handling  at  harvest  and  delay  in  placing  in  storage. 
Wounds,  bruises,  and  delay  in  placing  in  storage  greatly  increased 

the  subsequent  susceptibility  in  storage  of  pears  to  the  attacks  of  mold. 

5.  Cross-pollination. 

Cross-pollinated  Bartlett  pears  matured  earlier  than  self -pollinated 
specimens,  and  this  occasionally  indirectly  affected  the  keeping  quality. 

CONCLUSIONS    AND    RECOMMENDATIONS 

1.  Cold  storage  may  be  utilized  for  holding  temporarily  the  crop  of 
some  varieties  of  pears. 

2.  Low  temperature  was  an  important  factor  in  retarding  the 
ripening  of  pears  and  in  controlling  the  development  of  rot  organisms. 

3.  The  effect  of  degree  of  maturity  at  time  of  harvest  upon  the  size, 
flavor,  and  keeping  quality  was  found  to  be  marked.  Apparently 
there  has  been  a  tendency  to  harvest  many  pears  prematurely. 

4.  When  picked  two  weeks  after  the  commercial  harvest  period 
for  the  variety,  the  Beurre  Bosc,  Doyenne  du  Cornice,  and  Beurre 
Hardy  attained  a  "very  good"  to  "excellent"  quality  as  contrasted 
with  a  "fair"  to  "good"  quality.  The  fruit  was  also  of  larger  size 
and  had  a  more  attractive  apearance. 


54  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION 

5.  The  pears  susceptible  to  scald  showed  a  tendency  to  scald  first 
at  points  in  contact  with  the  sides  of  the  container  or  with  other  pears, 
indicating  one  important  advantage  of  aeration. 

6.  The  blue  mold  ( Penicillmm  sps.)  occurred  upon  certain  varieties 
of  pears  at  all  of  the  storage  temperatures  utilized.  The  lower  tem- 
peratures, however,  delayed  its  appearance  and  retarded  its  growth, 
as  for  example,  the  Easter  Beurre  at  36°  F.,  developed  blue  mold  by 
February  10,  but  at  32°  F.  had  developed  no  mold  as  late  as  May  1. 

7.  There  were  varietal  differences  in  susceptibility  to  ammonia 
fumes,  apparently  resulting  from  difference  in  size  and  number  of  the 
lenticel-like  openings  and  the  development  of  the  cutin. 

8.  The  average  loss  in  weight  of  Bartlett  pears  during  a  nine-day 
ripening  period  after  harvesting  was  about  five  per  cent,  this  loss 
resulting  chiefly  from  transpiration. 

9.  During  a  twenty-day  ripening  period  the  loss  in  weight  was 
greater  with  the  earlier  pickings  of  pears  than  with  the  later  pickings 
of  the  same  variety. 

10.  Data  indicated  that  when  properly  harvested  and  quickly 
stored  at  temperatures  of  30°  to  32°  F.,  the  Bartlett  from  certain 
sections  could  be  held  in  storage  for  several  weeks  and  still  be  in  good 
condition  for  canning. 

11.  Of  the  pears  studied  those  exhibiting  most  satisfactory  keeping 
qualities  in  storage  were  the  Doyenne  d  'Alencon,  Lawrence,  P.  Barry, 
Forelle,  Columbia,  Block  "18,"  Vicar  of  Winkfield  and  Winter  Nelis. 

12.  The  pears  unsuitable  for  storage  were  the  Madeleine,  Lawson, 
and  Bloodgood. 

13.  A  detailed  account  of  the  storage  behavior  of  each  of  forty- 
three  varieties  of  pears  is  presented. 

ACKNOWLEDGMENTS 

The  writers  desire  to  express  their  appreciation  to  the  following 
individuals,  who  at  one  time  or  another,  helped  in  harvesting  the  fruit, 
controlling  the  temperatures,  making  observations,  and  tabulating 
data:  Professors  G.  L.  Philp,  F.  W.  Allen,  and  Messrs.  R.  H.  Taylor, 
M.  J.  Heppner,  J.  L.  Quail,  and  V.  B.  Claypool.  The  writers  also 
wish  to  acknowledge  the  suggestions  and  kindly  help  received  from 
Dr.  J.  C.  Whitten  up  to  the  time  of  his  death. 

Especial  thanks  are  extended  to  Mr.  George  C.  Roeding  for  his 
kind  cooperation  in  permitting  fruit  to  be  harvested  from  the  variety 
collection  at  Niles.  Thanks  are  also  due  Mr.  V.  T.  McCurdy  of  Santa 
Clara,  for  his  cooperation  which  permitted  the  harvesting  at  different 
stages  of  maturity  of  the  Hardy,  Cornice,  and  Bosc. 


Bulletin  377]  THE  COLD  STORAGE  OF  PEARS  55 


BIBLIOGRAPHY 

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Bd.  Hort.,  359.     1892. 

4 Descriptions  of  Fruit  Growing  at  the  Agassiz  Experimental  Farm. 

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Pacific  Coast  States.    U.  S.  Dept.  Agr.  Bull.  1072:  1-16,  1  table.    1922. 
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1903. 


56  UNIVERSITY   OF   CALIFORNIA — EXPERIMENT   STATION 

22  Ramsey,  H.  J.,  McKay,  A.  W.,  Markell,  E.  L.,  and  Bird,  H.  S.    The  Handling 

and  Storage  of  Apples  in  the  Pacific  Northwest.     U.  S.  Dept.  Agr.  Bull. 
587:  1-32,  8  pis.,  5  tables.     1917. 

23  Sinclair,  J.   M.     Victorian  Fruit  in  London.     Jour.   Dept.   Agr.  Victoria  2: 

149-157.    1903. 

24  Stubenrauch,  A.  V.,  and  Eamsey,  H.  J.    Bartlett  Pear  Precooling  and  Storage 

Investigations  in  the  Rogue  River  Valley.     U.S.  Dept.  Agr.,  Bur.  Plant 
Ind.  Cir.  114:  19-24.    1914. 

25  Thomas,  J.  J.     The  American  Fruit  Culturist.     491-544,  figs.  636-735.     New 

York,  1911. 
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219-410,  186  figs,     1918. 

27  Wickson,  E.  J.    California  Fruits.     1-286.    San  Francisco,  1914. 

28  Wright,  R.  C,  and  Taylor,  G.  F.     The  Freezing  Temperatures  of  Some  Fruits, 

Vegetables,  and  Cut  Flowers.    IT.  S.  Dept.  Agr.  Bull.  1133:  1-8,  3  tables. 
1923. 


STATION  PUBLICATIONS  AVAILABLE  FOR  FREE  DISTRIBUTION 


No. 

253.  Irrigation  and  Soil  Conditions  in  the 
Sierra  Nevada  Foothills,  California. 

261.  Melaxuraa    of    the    Walnut,    "Juglans 

regia." 

262.  Citrus   Diseases   of   Florida   and   Cuba 

Compared  with  those  of  Califoruia. 

263.  Size  Grades  for  Ripe  Olives. 

268.  Growing  and  Grafting  Olive  Seedlings. 
273.  Preliminary  Report  on  Kearney  Vine- 
yard Experimental  Drain. 

275.  The  Cultivation  of  Belladonna  in  Cali- 

fornia. 

276.  The   Pomegranate. 

277.  Sudan  Grass. 

278.  Grain   Sorghums. 

279.  Irrigation  of  Rice  in  California. 

280.  Irrigation  of  Alfalfa  in  the  Sacramento 

Valley. 
283.  The  Olive  Insects  of  California. 

285.  The  Milk  Goat  in  California. 

286.  Commercial   Fertilizers. 

287.  Vinegar  from  Waste  Fruits. 
294.  Bean  Culture  in  California. 
298.    Seedless  Raisin  Grapes. 

304.  A  Study  of  the  Effects  of  Freezes  on 
Citrus  in   California. 

312.   Mariout  Barley. 

317.  Selections  of  Stocks  in  Citrus  Propa- 
gation. 

319.   Caprifigs  and  Capriflcation. 

321.   Commercial  Production  of  Grape  Syrup. 

324.  Storage  of  Perishable  Fruit  at  Freezing 

Temperatures. 

325.  Rice  Irrigation  Measurements  and  Ex- 

periments    in      Sacramento      Valley, 

1914-1919. 
328.   Prune  Growing  in  California. 
331.    Phylloxera-Resistant  Stocks. 

334.  Preliminary  Volume  Tables  for  Second- 

Growth  Redwood. 

335.  Cocoanut    Meal    as    a    Feed    for    Dairy 

Cows  and   Other  Livestock. 

336.  The   Preparation   of   Nicotine   Dust   as 

an  Insecticide. 
339.  The  Relative  Cost  of  Making  Logs  from 
Small    and    Large    Timber. 

343.  Cheese  Pests  and  Their  Control. 

344.  Cold  Storage  as  an  Aid  to  the  Market- 

ing of  Plums. 


BULLETINS 
No. 


347. 

348. 
349. 

350. 
351. 
352. 

353. 
354. 
355. 
357. 


358. 

859. 
360. 

361. 

362. 
363. 

364. 

366. 

367. 

368. 

369. 
370. 
371. 

372. 

373. 
374. 

3  75. 
376. 


Almond  Pollination. 

The  Control  of  Red  Spiders  in  Decidu- 
ous Orchards. 

Pruning  Young  Olive  Trees. 

A  Study  of  Sidedraft  and  Tractor 
Hitches. 

Agriculture  in  Cut-over  Redwood  Lands. 

California  State  Dairy  Cow  Competition. 

Further  Experiments  in  Plum  Pollina- 
tion. 

Bovine  Infectious  Abortion. 

Results  of  Rice  Experiments  in   1922. 

The  Peach  Twig  Borer. 

A  Self-mixing  Dusting  Machine  for 
Applying  Dry  Insecticides  and 
Fungicides. 

Black  Measles,  Water  Berries,  and 
Related   Vine   Troubles. 

Fruit  Beverage  Investigations. 

Gum  Diseases  of  Citrus  Trees  in  Cali- 
fornia. 

Preliminary  Yield  Tables  for  Second 
Growth  Redwood. 

Dust  and  the  Tractor  Engine. 

The  Pruning  of  Citrus  Trees  in  Cali- 
fornia. 

Fungicidal  Dusts  for  the  Control  of 
Bunt. 

Turkish  Tobacco  Culture,  Curing  and 
Marketing. 

Methods  of  Harvesting  and  Irrigation 
in  Relation  to  Mouldy  Walnuts. 

Bacterial  Decomposition  of  Olives  dur- 
ing Pickling. 

Comparison  of  Woods  for  Butter  Boxes. 

Browning  of  Yellow  Newtown  Apples. 

The  Relative  Cost  of  Yarding  Small 
and  Large  Timber. 

The  Cost  of  Producing  Market  Milk  and 
Butterfat  on  246  California  Dairies. 

Pear  Pollination. 

A  Survey  of  Orchard  Practices  in  the 
Citrus  Industry  of  Southern  Cali- 
fornia. 

Results  of  Rice  Experiments  at  Cor- 
tena,  1923. 

Sun-Drying  and  Dehydration  of  Wal 
nuts. 


CIRCULARS 

No.  No. 

70.  Observations   on    the    Status   of    Corn  161. 

Growing  in  California.  164 

87.  Alfalfa.  165. 

111.  The  Use  of  Lime  and  Gypsum  on  Cali- 
fornia Soils.  166. 

113.  Correspondence  Courses  in  Agriculture.  167. 

117.  The    Selection    and    Cost   of    a    Small  170! 
Pumping  Plant. 

127.  House  Fumigation.  172. 

129.  The  Control  of  Citrus  Insects.  173. 

186.  Melilotus   (ndica    as    a    Green-Manure 

Crop  for  California.  174. 

144.   Oidium  or  Powdery  Mildew  of  the  Vine.  178. 

151.  Feeding  and  Management  of  Hogs.  179. 

152.  Some  Observations  on  the  Bulk  Hand- 

ling of  Grain   in   California.  184. 

153.  Announcement  of  the  California  State  190. 

Dairy  Cow  Competition,   1916-18.  193. 

154.  Irrigation  Practice  in  Growing  Small  198. 

Fruit  in  California.  199. 

155.  Bovine  Tuberculosis.  201. 

157.  Control  of  the  Pear  Scab.  202. 

158.  Home  and  Farm  Canning. 

160.   Lettuce  Growing  in  California.  203. 


Potatoes  in  California. 

Small  Fruit  Culture  in  California. 

Fundamentals   of    Sugar   Beet   Culture 

under  California  Conditions. 
The  County  Farm  Bureau. 
Feeding  Stuffs  of  Minor  Importance. 
Fertilizing  California  Soils  for  the  1918 

Crop. 
"Wheat  Culture. 
Th-'    Construction    of    the    Wood-Hoop 

Silo. 
Farm    Drainage  Methods. 
The  Packing  of  Apples  in  California. 
Factors    of    Importance    in    Producing 

Milk  of  Low  Bacterial  Count. 
A  Flnck  of  Sheep  on  the  Farm. 
Agriculture  Clubs   in  California. 
A  Study  of  Farm  Labor  in  California. 
Syrup  from   Sweet  Sorghum. 
Onion  Growing  in  California. 
Helpful  Hints  to  Hog  Raisers. 
County   Organizations   for   Rural   Fire 

Control. 
Peat  as  a  Manure  Substitute. 


CIRCULARS — Continued 


No. 

205.  Blackleg. 

206.  Jack  Cheese. 

208.  Summary  of  the  Annual  Reports  of  the 

Farm  Advisors  of  California. 

209.  The  Function  of  the  Farm  Bureau. 

210.  Suggestions  to  the  Settler  in  California. 
212.   Salvaging  Rain-Damaged  Prunes. 

214.  Seed  Treatment  for  the  Prevention  of 

Cereal  Smuts. 

215.  Feeding  Dairy  Cows  in  California. 
217.  Methods   for   Marketing   Vegetables   in 

California. 

219.  The  Present  Status  of  Alkali. 

220.  Unfermented  Fruit  Juices. 

228.   Vineyard   Irrigation  in   Arid  Climates. 

230.  Testing  Milk,    Cream,    and    Skim    Milk 

for  Butterfat. 

231.  The  Home  Vineyard. 

232.  Harvesting    and    Handling    California 

Cherries  for  Eastern  Shipment. 

233.  Artificial  Incubation. 

234.  Winter  Injury  to  Young  Walnut  Trees 

during  1921-22. 

235.  Soil  Analysis  and  Soil  and  Plant  Inter- 

relations. 

236.  The  Common  Hawks  and  Owls  of  Cali- 

fornia   from    the     Standpoint   of  the 
Rancher. 

237.  Directions  for  the  Tanning  and  Dress- 

ing of  Furs. 

238.  The  Apricot  in  California. 

239.  Harvesting  and  Handling  Apricots  and 

Plums  for  Eastern   Shipment. 

240.  Harvesting    and    Handling    Pears    for 

Eastern    Shipment. 

241.  Harvesting  and  Handling  Peaches  for 

Eastern    Shipment. 

243.  Marmalade  Juice  and  Jelly  Juice  from 

Citrus  Fruits. 

244.  Central  Wire  Bracing  for  Fruit  Trees. 

245.  Vine  Pruning  Systems. 


No. 
247. 
248. 

249. 
250. 

251. 


252. 
253. 
254. 

255. 

256. 
257. 
258. 
259. 
260. 

261. 
262. 
263. 
264. 

265. 
266. 

267. 


269. 
270. 
271. 
272. 

273. 
275. 


Colonization   and  Rural  Development. 

Some  Common  Errors  in  Vine  Pruni»g 
and  Their  Remedies. 

Replacing  Missing  Vines. 

Measurement  of  Irrigation  Water  on 
the   Farm. 

Recommendations  Concerning  the  Com- 
mon Diseases  and  Parasites  of 
Poultry    in    California. 

Supports  for  Vines. 

Vineyard   Plans. 

The  Use  of  Artificial  Light  to  Increase 
Winter  Egg  Production. 

Leguminous  Plants  as  Organic  Fertil- 
izer in  California  Agriculture. 

The  Control  of  Wild  Morning  Glory. 

The  Small-Seeded  Horse  Bean. 

Thinning  Deciduous  Fruits. 

Pear  By-products. 

A  Selected  List  of  References  Relating 
to  Irrigation  in  California. 

Sewing  Grain  Sacks. 

Cabbage  Growing  in  California. 

Tomato  Production  in  California. 

Preliminary  Essentials  to  Bovine  Tuber- 
culosis Control. 

Plant  Disease  and  Pest  Control. 

Analyzing  the  Citrus  Orchard  by  Means 
of  Simple  Tree  Records. 

The  Tendency  of  Tractors  to  Rise  in 
Front;  Causes  and  Remedies. 

Inexpensive  Labor-saving  Poultry  Ap- 
pliances. 

An  Orchard  Brush  Burner. 

A  Farm  Septic  Tank. 

Brooding  Chicks  Artificially. 

California  Farm  Tenancy  and  Methods 
of  Leasing. 

Saving  the  Gophered  Citrus  Tree. 

Marketable  California  Decorative 
Greens. 


lOm-9,'24 


